Follistatin-344: The Definitive Guide

What is Follistatin-344?

Follistatin-344 is the name used online for follistatin, a natural human protein that blocks myostatin, a signal that limits how large muscles grow. People discuss it for building muscle, and researchers have tested it as a gene therapy for muscle-wasting diseases.

Follistatin is made from the human FST gene, and most of it in the blood comes from the liver. The gene's instructions produce a chain of 344 amino acids (the building blocks of proteins). Before the protein leaves the cell, the first 29 are cut off, leaving the working form of 315, called FS315. A shorter version made from the same gene, FS288, stays attached to cell surfaces. So "344" names the starting instructions, not a special drug. At about 35,000 to 38,000 daltons before sugars are added, follistatin is more than 20 times longer than BPC-157, a 15-amino-acid peptide. [1], [14], [15]

Follistatin was discovered in 1987 as a protein that lowers follicle-stimulating hormone (FSH), a hormone that drives fertility. It binds several related signals: myostatin, the activins and GDF11, a closely related growth signal. [16], [17], [2]

It is investigational: anti-doping scientists noted in 2019 that no approved follistatin medicine existed, and we found none approved since. [10], [18], [167]

Gene therapy or vial: which one is “Follistatin-344”?

The name covers two very different things. In medical research, "FS344" means the follistatin gene packaged inside a harmless virus and injected once into muscle, so the muscle makes follistatin itself for months or years. Online, "Follistatin-344" usually means a vial of freeze-dried protein sold for repeated injections. Every clinical trial of FS344 used the gene therapy. No study has tested the vials in people. [6], [7], [8], [10]

Doserly

Two things called Follistatin-344

What is injected

Gene therapy: The follistatin gene inside a modified virus (AAV1)
Vial: Freeze-dried follistatin protein, mixed with water

Where and how often

Gene therapy: Into thigh muscles, once
Vial: Usually into the fatty layer under the skin (subcutaneous), daily for about 10 days

How the amount is counted

Gene therapy: Vector genomes per kilogram (e.g. 6 × 10¹¹ per leg)
Vial: Micrograms (usually 100 mcg)

How long it lasts

Gene therapy: Muscle kept making follistatin for at least 15 months in monkeys
Vial: Not measured in people; in rats, blood levels halved in about 4 minutes, then about 2 hours

Tested in people?

Gene therapy: Yes: results reported for 15 patients with muscle diseases
Vial: No clinical trial; an 11-person eye-condition case series followed vial use

Can it be stopped?

Gene therapy: No: a one-time treatment that cannot be switched off
Vial: Injections can stop; what happens afterward has not been studied

What is inside

Gene therapy: Manufactured for clinical trials
Vial: Only 9 of 17 tested black-market products contained follistatin

Gene therapy results cannot be used as evidence for vials.

Typical Follistatin-344 Protocols

The most common protocol in the reviewed sources is 100 mcg once a day by subcutaneous injection for about 10 days, which uses exactly one 1 mg vial. Most pages place it inside a wider range of about 50–200 mcg a day for 10–30 days. [3], [4], [19], [20], [21], [22]

Before relying on any row: no amount in this table has been tested for safety in people, so no safe amount is known. [3], [13] The only published harm report linked to vials describes 11 bodybuilders whose eyesight worsened because fluid collected under the retina after they injected whole 1 mg vials; all three who had injected more than once had repeat episodes. Corticosteroid medicines, such as prednisone, are a major risk factor for the same eye condition, and the report does not say whether the men were also taking them. [9], [94] Only 9 of 17 black-market products tested contained follistatin, so the label may not match the vial. [10] Work out syringe units with the reconstitution calculator rather than copying them from someone else's protocol. Follistatin changes fertility hormones in animals, and it has not been studied in pregnancy, breastfeeding or anyone under 18. It is banned in sport at all times. [16], [124], [12] Full risks ↓

Titration Changing the amount in steps

Most pages keep one fixed amount for the whole course. One presents its lowest tier, 100 mcg a day for 10–14 days, as the place to start and check tolerance. Two others start higher and then reduce: 200 mcg a day for days 1–3, then 100 mcg a day for days 4–30; or daily injections for 7 days, then twice-weekly injections for 8–12 weeks. [5], [23], [22]

Breaks and cycles

Breaks are long compared with the courses. The source of the table above describes 20–30 days off after a 10-day course, 40–60 days after a 20-day course and 60–90 days after a 30-day course, with one to three courses a year. Others describe 3–4 weeks off, a 4-week break after a 10–20-day course, or at least 4–6 weeks. [5], [22], [4], [24]

Read the units: mcg means micrograms; 1 mg equals 1,000 mcg, so a 1 mg vial holds ten 100 mcg amounts. The amounts refer to follistatin protein as labelled on the vial, and testing has shown that labels can be wrong. Gene therapy doses are counted in vector genomes, not micrograms, and cannot be converted into a vial amount. [3], [10], [6]

Each row is a complete schedule from one source, so its amount and duration belong together. Low, mid and high are alternatives, not steps to move through. These schedules come from protocol websites rather than clinical trials: no study has given people injections of follistatin protein, so no tested human dose exists. [5], [13]

Where protocols differ: per injection or per day, breaks, muscle injections and units ↓

What is Follistatin-344 commonly used for?

People look into follistatin because they want more muscle than training and food alone seem to give them, or because they are losing muscle they want to keep. The hope is simple: switch off the body's brake on muscle growth.

That hope comes from striking animal results and a small number of gene therapy studies in people with muscle diseases. The sections below separate what people want from what has been shown. [27], [6]

Building muscle size and strength

This is the main reason follistatin appears in bodybuilding and fitness discussions. Mice bred to make extra follistatin in their muscles grew far larger muscles, with individual muscles weighing 194–327% more than normal in the most extreme mouse, and a one-time gene injection kept mouse muscles larger and stronger for more than two years. [27], [28]

In people without a muscle disease, two studies tested related products: an engineered follistatin drug, ACE-083, enlarged the injected muscle in healthy women without making it measurably stronger, and an uncontrolled company study of plasmid gene therapy reported about 2 pounds more lean mass on average. No study has tested vials. [43], [35] Public accounts from vial users mostly describe quick scale-weight gains and a "pumped" feeling, often during steroid cycles or very high-calorie eating, alongside many reports of no noticeable change. The experience section looks at these accounts in detail. [29], [30], [31]

Keeping muscle during weight loss

A newer interest is protecting muscle while losing weight, especially on GLP-1 (glucagon-like peptide-1) medicines such as semaglutide and tirzepatide, which can take muscle off along with fat. Drug companies are testing antibodies that act on the same pathway for exactly this purpose. Those are different, engineered medicines. No trial has tested follistatin itself for this. [32], [33], [34]

Muscle loss with ageing and "longevity" gene therapy

Some clinics outside the United States offer follistatin gene therapy as an anti-ageing treatment, and public figures have described having it. The best-known program gave one injection of follistatin gene material (plasmid DNA, a ring of DNA that cells can read) to 43 volunteers without a comparison group, and reported its own results without peer review. It is a different product again from the vials. [35], [36], [37]

Muscle-wasting diseases

The serious medical research has been in muscular dystrophies (inherited diseases in which muscle breaks down) and inclusion body myositis (a slowly progressive muscle disease of older adults). Researchers reported results of follistatin gene therapy in 15 patients, and a related engineered drug, ACE-083, in larger trials. None of these led to an approved treatment. [6], [7], [8], [38]

Other uses you may come across

Some pages also promote follistatin for fat loss, hair growth or injury recovery. No controlled human study has tested any of these; the company plasmid study reported a small fall in body fat without a comparison group. The other fat and metabolism findings come from mice, and the direction of the effect depends on the model. [35], [39], [40]

See the human study results or explore the animal research.

Where do Follistatin-344 protocols differ?

Almost every page agrees on 100 mcg as the typical amount, but the details around it vary: how often, into which tissue, for how long and with what break. Here is what those differences mean when reading a protocol.

Is the number for one injection or the whole day?

100 mcg twice a day is 200 mcg for the day. The table above keeps the amount each time and the daily total in separate columns for that reason. [5]

Pages that describe injections into muscles add another layer. One lists 100–200 mcg "per site" every other day into both arms or both thighs, so a single injection day uses 200–400 mcg in total. Another gives 150–400 mcg for injections into a muscle without a clear frequency. Check whether a number means per injection, per muscle, per day or per week before comparing it with anything else. [24], [41]

Once a day, every other day or twice a week?

Daily injections are the most common pattern. Some pages use every other day for the same 10–30-day course, and a few use twice-weekly injections for 8–12 weeks. One page recommends 100 mcg into the target muscle twice a week without a course length. Spreading injections out changes the total amount over a course, and none of these frequencies has been compared in people. [22], [4], [42]

Should it be taken in the morning or after training?

Pages disagree without data either way. One says most protocols use morning injections; another prefers after workouts; a third limits injections to training days only. No study has tested timing. [5], [4], [41]

Do sources start low, or start high and reduce?

Most use one fixed amount. The two stepped schedules in the titration notes above both front-load. One page says a higher start "saturates" myostatin faster, then says it is debated whether this changes anything. No page ties either schedule to measured blood levels. [23], [22]

How many days, and how long is the break?

Courses of 10–30 days are short compared with most peptides, and breaks are often longer than the course itself. [5], [22], [24] Pages explain the long breaks by cost, missing long-term safety data and possible effects on fertility hormones. Those are reasons for caution, not evidence that a particular break length works. [5]

Into the belly or into the muscle you want to grow?

Most schedules use subcutaneous injections into the belly, thigh or upper arm. A separate group of pages describes intramuscular injections (into a muscle) on both sides of the body, into the biceps, thighs or calves, on the idea that follistatin acts where it is injected. [5], [24], [20]

An engineered follistatin drug did grow only the muscles it was injected into, but no study has tested this with vials. The route chapter explains why. [43]

FS344 or FS315 vials?

Some sellers offer "Follistatin 315" as a separate product with nearly the same protocols (often 100 mcg a day for 10 days, or 100–300 mcg a day for 4–8 weeks). Because FS344 is the precursor of FS315, a product labelled 344 would, if accurate, still carry the 29-building-block front section that the body normally removes. Tested black-market "344" products that did contain follistatin were a lab-tagged form, not the body's own version. [44], [45], [1], [10]

One 2026 dosing page says injected FS344 splits into both FS315 and FS288. That is not how FS288 is made: it comes from a differently spliced copy of the gene's message, not from cutting up FS344. [169], [1]

Why do some pages list vector genomes or "1 mg"?

Some pages print the gene therapy amounts (for example, 6 × 10¹¹ vector genomes per kilogram per leg) next to microgram protocols, or list "1,000 mcg" because the people in the eye-condition case series injected whole 1 mg vials. The first is a count of virus particles, not a protein amount; the second is a harm report, not a dose. Neither is a protocol. [46], [26], [9]

What do community education groups describe?

Two courses in the community education groups we reviewed print an amount: 100 mcg once daily in the morning, or 100–300 mcg once daily around training. Neither gives a course length, and one listed it as an optional add-on that its own full schedule never includes. The educators themselves mostly rank follistatin as a low-evidence, last-resort option. The experience section explains more.

How do micrograms convert to syringe units?

Many people meet "units" on an insulin syringe. A U-100 syringe has 100 units per millilitre, so units measure volume, not an amount of follistatin. How much follistatin each unit holds depends on how much liquid was added to the vial.

For example, a 1 mg (1,000 mcg) vial mixed with 2 mL gives 500 mcg per mL, or 5 mcg per unit, so 100 mcg would be 20 units. Mixed with 1 mL instead, the same 100 mcg is 10 units. That is why a number of units copied from someone else's protocol can be wrong. Doserly's reconstitution calculator works this out for any vial and shows each step. [3], [5]

What happens when you stop Follistatin-344?

This has not been studied for vials. No human study has looked for withdrawal effects or a rebound after stopping injected follistatin, because no human study has given it. That is an absence of data, not proof that nothing happens. [13], [5]

• The closest human evidence is short. In healthy women given ACE-083 into one muscle, muscle volume was still higher 8 weeks after the last dose at the highest amounts, but the difference was no longer statistically significant. In the dose groups tested, the drug was detectable in the blood only during the first day after dosing. ACE-083 is an engineered drug, so this does not show what happens after stopping a vial. [43]
• Gene therapy cannot be stopped. It is a one-time treatment. In monkeys, the injected muscles kept making follistatin for at least 15 months, and in mice the effect lasted more than two years. There is no way to switch it off if a problem appears. [49], [28]
• Animal protein studies are thin. In mice given follistatin genetic instructions (mRNA) in tiny particles, blood follistatin stayed raised for about three days after each injection and then fell back. In rats, researchers speculated, without testing it, that stopping local follistatin might speed muscle breakdown. [50], [51]
• Websites contradict each other. One vendor publishes one page saying gains reverse within 4–6 weeks of stopping and another saying there is no rebound. Neither cites human data. [52], [53]
• Community accounts point both ways. Some forum users said they kept their gains, though one partly credited the steroids he was taking at the same time and another had also taken ACE-031. Others said the early gain was mostly water, or that they kept nothing. [54], [129], [30], [55]

The long breaks protocols describe are a source convention based on cost and caution, not a response to known withdrawal effects. [5]

Do injected follistatin, gene therapy and ACE-083 behave the same way?

No. They start in different places and last for very different lengths of time, which is why results from one cannot be carried over to another.

• Subcutaneous injection of a protein vial puts follistatin into the fatty layer, from where it has to reach the blood. This is what most websites describe. [5]
• Intramuscular injection (into a muscle) of a protein vial is described by a minority of pages that want a local effect. [24]
• Gene therapy injects the follistatin gene, carried by a modified adeno-associated virus (AAV), into muscle once. The muscle cells then make follistatin themselves. [6]
• Plasmid gene therapy injects a ring of DNA carrying the gene into belly fat once; the company that ran it says the tissue then makes follistatin for a period. [35]
• Intravenous (IV) injection (into a vein) has been used only in animal studies of follistatin protein. [13]

Doserly

How long each form lasts

Log scale · 1 min · 1 hour · 1 day · 1 week · 1 month · 1 year

Native follistatin protein

1. Native follistatin injected into a vein (rats)Animal study

   half-life about 4 minutes, then about 131 minutes

Engineered drugs in the same pathway

1. ACE-083, engineered follistatin, injected into muscle (people)Human trial

   detectable in blood only on the first day after a dose

2. ACE-031, a different drug in the same pathway (people)Human trial

   half-life 10–15 days

3. Apitegromab, approved antibody in the same pathway (people)Label

   half-life about 31 days (label)

Gene therapy

1. Follistatin gene therapy into muscle (monkeys)Animal study

   still making follistatin at 15 months

2. Follistatin gene therapy (mice)Animal study

   larger, stronger muscles for more than 2 years

Half-life of a follistatin vial has never been measured in people. Values come from different species and molecules and are not interchangeable.

Native follistatin is cleared quickly in animals. In rats, follistatin injected into a vein collected in the liver more than in any other organ measured. Researchers who later redesigned the protein wrote that native follistatin is "poorly suited" to work as an injected drug throughout the body, and that fast clearance through the liver, helped by its tendency to stick to cell surfaces, "limits its therapeutic potential". Their fix was to engineer new versions that last longer; those versions have not been tested in people and are not what vials contain. [13], [56], [57]

Bioavailability, the share of a dose that reaches the blood in a usable form, has never been measured for a follistatin vial in people. The only direct data on raising blood levels with injected follistatin protein come from mice. Daily injections of FS288 for 13 weeks significantly raised blood follistatin and lean mass only at the highest of three amounts tested: 100 micrograms a day. The two lower amounts did not raise blood levels significantly and reduced fat only by the end of the study. That highest amount is the same number websites give a full-grown adult, who weighs thousands of times more than a mouse. This is not a human dose; it shows how little the online amounts are anchored to evidence. [58]

How long does follistatin last in the body?

Half-life is the time it takes for the level in the blood to fall by half. It is not how long an effect lasts.

No one has measured it in people. In the one published study of follistatin injected into a vein, in rats, blood levels fell by half in about 4 minutes during a fast first phase and in about 131 minutes (a little over 2 hours) during a slower second phase. Websites quote half-lives from about 1 hour to 8–12 hours, and one describes the body's own follistatin as lasting 10–15 hours; none of them cites a human measurement. [13], [59], [60], [46]

Engineered relatives last much longer by design. ACE-031, a different drug that blocks the same pathway, had a half-life of 10–15 days in healthy volunteers, and apitegromab, an approved antibody in the same pathway, has a label half-life of about 31 days. Those numbers belong to those drugs, not to follistatin. [61], [62]

A short half-life does not by itself prove that a daily 100 mcg injection does nothing. It does mean that the long-lasting effects seen with gene therapy, which keeps muscle making follistatin day and night, cannot simply be carried over to protein injections. [49], [13]

Does injecting into one muscle make that muscle grow?

With engineered drugs, yes; with vials, nobody knows. ACE-083, a version of follistatin fused to part of an antibody so that it stays near the injection site, enlarged only the muscles it was injected into, and a similar engineered form did the same in mice. Native follistatin from a vial is a different molecule, and no study has tested whether a small vial injection grows the muscle it goes into. [43], [63]

Is there a follistatin pill or nasal spray?

No product has been tested. Follistatin is a large protein, and one page selling a related form says itself that absorption by mouth is poor. Supplements such as epicatechin are sometimes marketed as raising follistatin; the questions section covers them. [45]

How should Follistatin-344 be stored, and how long does it last?

We found no published stability study of the vials sold as Follistatin-344, so storage advice comes from sellers and protocol pages, not from a tested medicine label.

• Powder, before mixing. Pages disagree. Most say to keep the freeze-dried powder frozen at −20 °C (one adds "away from light"), while another says the powder is stable at room temperature. [3], [24], [64], [23]
• After mixing. Once the powder is mixed with liquid (reconstituted), pages give very different limits at 2–8 °C (fridge temperature): "days to a couple of weeks", "1–2 weeks at most", 7–14 days, up to 2 weeks, 14–21 days, or 28 days. The shorter limits come from pages that point out follistatin is a large, fragile protein rather than a small peptide. [3], [24], [169], [42], [5], [64]
• Freezing and light. Most pages say never to freeze the mixed solution; another suggests freezing single-use portions for longer storage. [3], [5], [24], [64], [42] Several pages advise keeping the vial away from light before and after mixing. [3], [24], [42], [169]

None of these limits has been tested on a retail vial; they are seller and website claims, not expiry dates.

Tested black-market vials also contained a large share of clumped protein (aggregation); product quality covers what that means. This guide does not cover mixing or injection technique; the Academy note below covers practical handling. [10]

What do we actually know about Follistatin-344 in people?

The human evidence comes in three groups, and none of them tested the vials sold online: gene therapy in people with muscle diseases, an engineered follistatin drug called ACE-083, and company-run gene therapy offered as an anti-ageing treatment. A fourth kind of evidence, a case series of eye problems in bodybuilders, is covered in the risks section.

Doserly

Who has received a follistatin-based treatment in a study

Gene therapy (AAV1-FS344)

Becker muscular dystrophy

6No comparison group

Inclusion body myositis

6Historical comparisona further 3 in a low-dose group were never reported

Duchenne muscular dystrophy

3No comparison group

Engineered drug (ACE-083)

Healthy women

42Placebo-controlled+ 16 placebo

Facioscapulohumeral muscular dystrophy

95 enrolledPlacebo-controlled, then open-label

Charcot-Marie-Tooth disease

63 enrolledPlacebo-controlled, then open-label

Plasmid gene therapy (company)

Volunteers aged 23–88

43Company-run, not peer reviewed

Harm report after vial use

Eye condition (CSCR) in bodybuilders

11Case series

Protein vials

Follistatin-344 vials in any study

0 peopleNo study

Numbers are people who received the treatment (trial totals where marked 'enrolled'). No row is a test of the vials sold online.

What did the human studies find?

Across the gene therapy trials, one research team reported results for 15 people, with no placebo group. They show short-term tolerance and larger muscle fibres in some patients, not restored function, and nothing about vials. [6], [7], [8], [67]

What did the gene therapy trials measure?

In the Becker study, each leg received AAV1 carrying the FS344 gene, at 3 × 10¹¹ or 6 × 10¹¹ vector genomes per kilogram per leg. There were no side effects the researchers linked to the gene transfer, reproductive hormones stayed normal, and two patients showed an immune-cell response against follistatin itself. [6]

The myositis trial used the same product with an exercise program and prednisone (60 mg a day) for a month beforehand. In their reply to the critic, the authors wrote that a combined effect of treatment and exercise was "more realistic". A lower-dose group listed in the trial registry never appeared in either paper. [68], [65], [67]

The US regulator granted the gene therapy orphan designations (a status that supports research into rare diseases) for Duchenne and Becker muscular dystrophy in 2012 and for inclusion body myositis in 2016. A designation is not an approval, and the program did not reach one. [69], [70]

What happened with ACE-083, the injected follistatin drug?

ACE-083 was follistatin joined to part of an antibody so that it would stay in the injected muscle. It is the closest thing to "injected follistatin" ever tested in people, and it worked as designed on muscle size: injected muscles got measurably bigger. [43], [71]

It did not reliably make people stronger or more capable. Each patient trial found a strength gain on one measure, but not consistently. The two trials were stopped because they "did not achieve functional secondary endpoints", and the long-term extension study was terminated too. Many patients also developed anti-drug antibodies, antibodies against the drug itself: about 39% in one trial and 48% in the other. [72], [73], [74], [38], [66]

What about the anti-ageing gene therapy clinics?

A company ran a study in which 43 volunteers aged 23 to 88, at a clinic in a special economic zone in Honduras, received one injection of follistatin plasmid DNA (50 micrograms of DNA, not protein) into belly fat. There was no comparison group, the study was registered only after it had finished, and the report was written by company staff and not peer reviewed. [35], [36]

It reported that blood follistatin rose from 8.58 to 24.03 ng/mL and lean mass by about 2 pounds (1.96 lb) on average, with no severe side effects. Low-density lipoprotein (LDL) cholesterol, the kind linked to heart disease, rose by an average of 8 mg/dL overall, which was not statistically significant, and by an average of 19 mg/dL in about a third of participants. [35]

A well-known self-experimenter who had the treatment published that his follistatin levels rose 160% and his muscle mass 7%, while following many other diet, exercise and drug routines at the same time. A newer trial of an AAV9 follistatin gene therapy for age-related muscle loss is recruiting in Honduras. [37], [47]

Does bigger muscle mean stronger or more capable?

Not necessarily, and this is the most important lesson from the research. Muscle size, strength and everyday function are separate outcomes. A scan can show a bigger muscle; only a strength or function test shows whether a person can do more with it.

ACE-083 enlarged muscles without consistent gains in strength or function. The gene therapy trials reported better walking in some patients, but without a proper comparison group. Across the wider class of drugs that block myostatin or activin, muscle mass rose more reliably than function. [43], [38], [75]

For someone tracking their own results, the same logic applies: useful records separate weight, measured lean mass, strength numbers and how everyday tasks feel, because a quick gain on the scale can be mostly water. [54], [30]

Why is there no approved follistatin medicine?

Drug companies have tried this pathway many times, mostly with engineered antibodies and receptor decoys rather than follistatin itself, and the pattern is consistent: muscle mass goes up, function often does not. [75], [76]

• Bimagrumab, an antibody against the receptor myostatin uses, did not improve walking in inclusion body myositis. In an obesity trial with semaglutide it helped preserve lean mass, but physical functioning scores were similar across groups. [77], [32]
• Domagrozumab, an anti-myostatin antibody, did not improve a stair-climb test in Duchenne muscular dystrophy, and the studies were stopped. Landogrozumab added a little lean mass in older people who fall, with mixed results on function. [78], [79], [80]
• Apitegromab (ISEMBYLD), an antibody against the inactive form of myostatin, became on September 11, 2026 the first drug in this pathway approved by the US regulator to target muscle loss: spinal muscular atrophy, alongside standard treatment, as an IV infusion of 10 mg per kilogram every four weeks. It is not follistatin, and its approval says nothing about vials. [81], [62]

How might follistatin build muscle?

Follistatin works by catching signal proteins outside cells before they reach their receptors. The most important one for muscle is myostatin, but it is not the only one, and that is the source of both its power in animal studies and its risks. [1], [2]

What is myostatin, and what happens without it?

Myostatin is a protein made by muscle that tells muscle to stop growing, a built-in brake. Mice without working myostatin have much larger muscles, and follistatin-rich mice grew even larger ones, which showed that follistatin blocks more than myostatin alone. [27], [82]

The same brake works in people. A child born with a mutation that disabled myostatin had unusually large muscles, a case reported in 2004, and natural myostatin mutations in cattle, sheep and dogs produce heavily muscled animals. Mice engineered to lack myostatin carry about twice the normal muscle mass. [83], [82]

Mice lacking myostatin that also made extra follistatin had about four times the muscle mass of normal mice. That showed follistatin releases more than one brake at once. [82]

How does follistatin block it?

Follistatin wraps around its targets and covers the part that would bind the receptor on the cell. Different sections of the protein handle different targets: one section binds myostatin more strongly, another activin. Researchers could change these sections to make follistatin favour one target over the other. [2], [1]

Its targets include myostatin, the activins (signals that also regulate fertility hormones, healing and scarring), GDF11 and some bone morphogenetic proteins. That broad reach is why follistatin is described as "not selective": it switches off several signals at once. [1], [2]

Is it only about myostatin?

No. In mice, follistatin still enlarged muscles when myostatin was absent, and the growth depended on a muscle-building pathway called mTOR and on the insulin-like growth factor-1 (IGF-1) receptor. Other mouse studies found it increased the stem cells that help muscles grow and repair (satellite cells). [84], [85], [86], [87]

These are animal findings. They explain why researchers are interested, not what a vial does in a person.

Where does the body's own follistatin come from?

Most follistatin in the blood comes from the liver, and its level rises and falls with the balance of the hormones glucagon and insulin. Blood levels rose about sevenfold after three hours of hard cycling, peaking a few hours into recovery, and they also rise during fasting and pregnancy. A higher blood level is a normal response to these states, not a sign of muscle growth. [15], [88], [89], [90]

Why do fertility hormones come up?

Follistatin was first discovered because it lowers FSH, a hormone that drives egg and sperm production, and it does so partly by blocking activin, which helps control FSH. That is why fertility is one of the main open safety questions. Could it affect fertility or hormones? covers what is and is not known. [16], [91], [92]

What are the risks and unanswered questions?

Is Follistatin-344 safe?

Its safety in people has not been established, and the one published human harm report tied to vials involves the eyes. No study has given people follistatin protein from a vial, so there is no measured rate of side effects, no known safe amount and no long-term data. [9], [13]

The gene therapy trials reported no serious side effects linked to the treatment, and the ACE-083 trials found it generally well tolerated apart from common injection-site reactions. Those results are real, but they come from different products, small numbers of people and close medical supervision. They cannot be carried over to a vial of uncertain content injected at home. [6], [7], [43]

Fifteen gene therapy patients without treatment-linked serious side effects is useful information, but studies that small and short miss uncommon and slow problems.

What is the eye problem linked to Follistatin-344?

A group of eye doctors in Turkey described 11 male bodybuilders who came to their clinic with worse eyesight after injecting follistatin-344. Scans showed central serous chorioretinopathy (CSCR): fluid collecting under the retina, the light-sensing layer at the back of the eye. [9]

• Every one of them had injected a whole 1 mg vial subcutaneously into the belly. Eight had injected once; three had injected more than once.
• Ten had it in one eye, one in both.
• In the eight who injected once, the fluid cleared and symptoms settled after about 2.3 months on average.
• All three who had injected more than once had repeat episodes. The summary does not say whether they injected again after the first one.

The authors concluded that follistatin-344 injection "can be considered as a risk factor" for CSCR. A conference report from the same doctors described three men aged 24 to 31 who came to the clinic about 20 days to a month after injecting a single vial, with reduced vision that had started 3 to 10 days earlier; they are probably among the 11. [9], [93]

This is an uncontrolled report, and it has real limits. Only its summary is publicly available, so it is unknown whether the men also used other drugs, and corticosteroid medicines such as prednisone were the strongest risk factor for CSCR in a study of 312 patients. Nobody knows what the vials actually contained. The report cannot show that follistatin caused the condition or how often it happens. It is still the only published human harm signal from the product people actually buy, and repeat episodes in all three repeat users are hard to dismiss. [9], [94], [10]

None of the public forum threads we reviewed included a first-hand account of vision changes, and neither did the community education groups. That absence cannot show how often eye problems happen.

What side effects do users describe?

In the public forum and Reddit accounts we reviewed, many complaints concerned the injection itself: painful, red, itchy or swollen lumps that sometimes lasted days, and in a few cases red streaks spreading from the site. Several people described flu-like symptoms, fever or shivering, fatigue, and joint or tendon pain, and some stopped because of them. One person described a severe reaction with a large rash, dizziness, fever and weakness after a single 100 mcg injection that improved over the next day. [97], [98], [99], [95], [100], [96]

These are personal accounts from people using products of unknown identity and purity, often alongside other drugs. They cannot tell us how often reactions happen or whether follistatin, a contaminant, another ingredient or the injection itself caused them. The ACE-083 trials also found injection-site reactions common, including in people given placebo. [10], [101], [72]

Could it affect fertility or hormones?

It is a reasonable question with no human answer for vials. Follistatin was discovered because it lowers FSH, and in animals too much or too little follistatin disrupts reproduction. In the 12 gene therapy patients who were checked, reproductive hormones stayed normal; the company plasmid study reported no fall in luteinizing hormone (LH), a hormone that drives testosterone production, or FSH. No one has measured hormones or fertility after repeated protein injections. [16], [102], [103], [6], [35]

A related drug gives a sense of how regulators treat this pathway: the label for sotatercept, an approved medicine that traps activins, warns that it may impair female and male fertility based on animal findings, and can harm an unborn baby. [104]

Does it affect the heart, tendons or blood vessels?

These worries come up often in user discussions, and they have not been studied in people taking follistatin. [29]

• Heart: no human data. In diabetic mice, extra follistatin reduced heart scarring but also enlarged the heart muscle, and pigs engineered to make human follistatin in muscle had no reported heart enlargement. [105], [106]
• Tendons: some users describe tendon and joint pain or feeling that training "wear and tear" increased. Tendon effects of blocking this pathway have been studied only in animals: tendons of mice born without myostatin were smaller, had fewer cells and were stiffer and more brittle, while in rats without myostatin, tendons stretched about 20% less before failing but were no smaller, weaker or stiffer. No study has looked at tendons in people using follistatin. [107], [108], [109], [110]
• Blood vessels and bleeding: broader drugs in this pathway caused nosebleeds and small visible blood vessels (telangiectasia). ACE-031 was stopped in boys with Duchenne muscular dystrophy for this reason, and on the sotatercept label nosebleeds affected 22.1% of patients against 1.9% on placebo. These drugs block activin, as follistatin does, but no human data show that follistatin causes these effects. [111], [104]

What did drug companies see with similar drugs?

The wider class carries safety signals worth knowing, even though none has been shown for follistatin itself. [75]

• Apitegromab (approved 2026 for spinal muscular atrophy) carries a warning for fractures: 5 of 53 patients (9%) had fractures on the drug against 1 on placebo (2%). [62]
• Trevogrumab plus garetosmab, two antibodies tested with semaglutide for weight loss: 28.3% of people on the three-drug combination stopped because of side effects, against 4.6% on semaglutide alone, and two people in the combination group died (the company did not attribute the deaths to the drugs). [33]
• Sotatercept, approved for a lung-blood-vessel disease, lists increased red blood cells, low platelets and serious bleeding among its warnings. [104]

Could product quality change the risk?

Yes, and it may be the biggest practical risk. When anti-doping chemists tested 17 black-market products sold mostly as "follistatin 344", only 9 contained follistatin. Some of the others contained different growth-promoting peptides, such as MGF or GHRP-2. All nine genuine products carried a laboratory tag (a His-tag) and contained a high proportion of clumped molecules. [10]

Follistatin is a large protein that has to be made in living cells, such as bacteria or animal cells, rather than assembled chemically like short peptides. One laboratory supplier's follistatin, for example, is made in bacteria, labelled "For Research Use Only" and sold with an endotoxin limit; that specification says nothing about vials sold as Follistatin-344. [112] Members of the community education groups repeatedly raised this worry: protein made in bacteria can carry bacterial toxins (endotoxin), and we found no published endotoxin test of these vials.

Is Follistatin-344 legal? Is it FDA-approved?

Checked September 23, 2026. Rules differ by country and change quickly.

United States. Follistatin is not an FDA-approved medicine, and FDA has told a pharmacy that it did not qualify for compounding:

• 2020. FDA warned a compounding pharmacy that had made products with follistatin that the substance had not been nominated for the list of ingredients pharmacies may use. [18]
• Protein rules. Because follistatin is longer than 40 amino acids, US regulations class it as a protein, which makes it a biological product. [113]
• 2026. It does not appear on FDA's May 2026 list of ingredients under review for compounding. An FDA briefing in 2026 mentioned "Follistatin-344" only as part of "regenerative combo" products promoted online. [114], [115]

Canada. Health Canada's Drug Product Database lists no product containing follistatin. Its April 2026 advisory on injectable peptides bought online does not name follistatin, but it states that "research use only" labelling "does not make these products legal". [167], [116]

Australia. Follistatin is a prescription-only (Schedule 4) substance and is also listed in Appendix D, clause 5 of the Poisons Standard, which makes possessing it without authority illegal. [11]

United Kingdom and European Union. Anti-doping scientists reported in 2019 that no approved follistatin medicine existed, and we found no UK or EU authorization since, nor any follistatin-specific statement from their medicines regulators. [10]

Is Follistatin-344 banned in sport? Does it show up on a drug test?

Yes, it is banned. The World Anti-Doping Agency's 2026 list prohibits "myostatin-binding proteins (e.g. follistatin…)" at all times, in and out of competition, under category S4.3. The 2027 list, which takes effect on January 1, 2027, keeps it. Follistatin has been named on the list since 2019, and drugs that change myostatin function were banned from at least 2008. Gene therapy used to enhance performance is separately banned as gene doping. [12], [117], [118], [119]

Anti-doping chemists published a blood and urine test in 2019 for tagged follistatin. All nine follistatin-containing products they examined carried a laboratory tag, which let the test tell them apart from the body's own protein; the paper does not show a way to do that for an untagged product. Laboratories have also developed tests for the follistatin gene used in gene doping. How long vial use remains detectable has not been published, and we found no public confirmation of routine testing for it. [10], [120]

Does follistatin cause cancer?

Nobody knows, and the animal and cell research points both ways. Follistatin reduced the spread of breast and lung cancer in mouse models, but ovarian cancer cells used follistatin to resist chemotherapy, and high follistatin in patients' ovarian tumours went with worse survival. No long-term cancer study of follistatin vials exists. [121], [122], [123]

Who should be especially cautious?

These groups have no safety data in people. That is a reason for caution, not proof of harm.

• Pregnancy, breastfeeding and trying to conceive. Follistatin affects fertility hormones and pregnancy in animals, and the related drug sotatercept carries a warning for harm to an unborn baby. [124], [104]
• Anyone with past eye problems, especially CSCR. The only human harm report involves this condition. [9]
• People using steroids. Corticosteroid medicines such as prednisone are a major risk factor for CSCR. Many vial users also take anabolic steroids, and the eye case series does not say which other drugs the men used. [94], [9], [54], [125]
• A history of cancer. Because of the mixed animal findings above. [123]
• Under 18. No studies include young people. This guide is written for adults.
• Competitive athletes. It is banned at all times. [12]
• People taking other medicines. Interactions have not been studied; see the next question.

Has Follistatin-344 been tested alongside other medicines?

Not in people. No study reports how follistatin interacts with prescription medicines, and the pages that list interactions offer opinions, not data. The gene therapy trials gave prednisone around treatment to calm the immune response, which says nothing about combining a vial with other drugs. Bring a complete list of everything you take to a pharmacist or doctor. [6], [7]

What should be monitored while using Follistatin-344?

There is no official monitoring plan, because no regulator has approved a follistatin product or written a label for it. What exists is a record of what the gene therapy and ACE-083 studies measured, and the signals seen in related drugs. It can help you prepare questions for a clinician; it is not a personal testing plan. [6], [43]

What did the studies check?

• The gene therapy trials took blood at the start, at days 7, 14, 30, 60, 90 and 180, and at one year: a complete blood count, liver and kidney tests, amylase (a pancreas enzyme), creatine kinase (a muscle enzyme) and the hormones FSH, LH, oestrogen and testosterone. They also tested for immune reactions against the virus and against follistatin. [6]
• The Duchenne gene therapy study added heart tests before treatment (an electrocardiogram and an ultrasound of the heart), plus urine tests, clotting tests and blood follistatin levels, with visits for two years. [126]
• The ACE-083 trials checked blood counts, blood chemistry, urine, heart rhythm, vital signs, muscle volume on MRI scans and anti-drug antibodies. [43], [38]
• The company plasmid study tracked blood follistatin, body composition by a low-dose X-ray scan (DEXA), LH and FSH, cholesterol, blood sugar markers and an inflammation marker (hs-CRP). [35]
• The eye cases were diagnosed with an eye scan (optical coherence tomography). No eye-screening schedule has been tested for follistatin users. [9]

Which signals matter, and why?

The cholesterol finding comes from an uncontrolled company study of gene therapy, and the bleeding and fracture signals come from different drugs. They show what researchers and regulators paid attention to, not what a person using a vial will experience. [35], [62], [104]

A blood follistatin test is not a practical way to monitor vial use: levels rise naturally with exercise and fasting, and no study has shown that a result tracks muscle growth after a vial. Why a blood test cannot confirm it is working. [127], [88], [89]

What do people in public communities report?

Public discussions of follistatin are dominated by questions, plans and sourcing requests; first-hand results are fewer than the attention suggests. The accounts that exist include quick scale-weight gains, no noticeable change, and injection reactions that made people stop. Most come from people also using steroids, growth hormone or other peptides. [29], [31], [98]

What do the positive reports look like?

The typical positive account describes a fast rise in scale weight, strong "pumps" in the gym and fuller-looking muscles within one or two weeks. One person logging a 10-day course of 100 mcg a day, injected into muscle, in 2011 went from 178 to 183 lb within five injections and then stopped gaining. He had no body-composition test, was in week 8 of a testosterone cycle and was eating about 4,000 calories a day. [25]

Another person on Reddit said they gained 10 pounds of lean muscle in 20 days on 100 mcg a day and later lost only 2 of them, while also on testosterone replacement (150 mg a week) and eating a lot, and without describing how lean mass was measured. A person on a modest routine of two injections a week for five weeks described fuller arms and a "modest" effect, while also training harder and paying more attention to diet. [128], [29]

How long did those changes last?

Follow-ups often change the story. One person who gained 8 pounds in the first two weeks said nothing more happened after that and stopped at three and a half weeks. Retelling it about a year and a half later, he said the gain was mostly lean and he kept it, but that he had started testosterone and another steroid first, so follistatin could not take all the credit. Another said he gained 7 pounds in the first week, "water mostly", and little after that. A third, who took ACE-031 at the same time, said he kept a little weight gained over the next six months, and that he was "very ill and very sore". [30], [54], [129]

These accounts cannot provide an average result or time course. They involve different products, amounts and drug combinations, and people with dramatic stories are more likely to post.

Does everyone describe an improvement?

No. Many people reported nothing: one gained no weight or strength after a week, another had "no effect" after trying twice, a third, who had tried both 344 and 315 years earlier, said he gained and kept nothing, and one commenter wrote that "every bb'er I know that has taken it saw little to no effect". Several suspected their product was fake. [130], [31], [131], [55]

People who had gene therapy also split. Some described gaining 8 to 11 pounds of muscle over a few months, usually without published scan results and sometimes with a commercial link to the treatment; another person who had a follistatin gene therapy abroad later wrote that they "did not get much of anything noticeable" from it. [132], [133], [134]

What about unwanted effects?

The same reports described in the risks section recur here: injection-site reactions, flu-like symptoms, fatigue and joint or tendon pain, with some people stopping because of them. [135], [109], [136]

What do community education groups say?

In the community education groups we reviewed, follistatin is discussed far more than it is used. Educators mostly rank it as a low-evidence, last-resort option, pointing to its short time in the body, its effects on activin and fertility hormones, and the gap between gene therapy results and vials. Only a handful of members described their own results, and those were brief: a small benefit that did not seem worth the price, or no noticeable effect.

Many members said they had bought a vial and never started, citing cost, doubts about what the vial contained or worries about the heart and fertility. More of the first-hand accounts concerned branded products marketed as "modified" or longer-acting follistatin, sold by single sellers without published data on what they contain; the gains described were not measured, and some came from people with a commercial interest in the product. None of the groups discussed the published eye-condition case series.

How can you judge a muscle-gain story?

Useful questions to ask: What exactly was used, from where, and was it tested? How much, how often and for how long? What else changed at the same time: steroids, growth hormone, calories, training? Was the gain measured as scale weight, a body-composition scan or a strength number? What happened a month after stopping?

A quick jump on the scale can come from water and heavy eating rather than muscle, and one long-time forum member put his own early gain down mostly to water. [54] A story with a scan, a strength log and a follow-up tells you far more than "I gained 10 pounds".

How does Follistatin-344 compare with IGF-1 LR3, PEG-MGF and MK-677?

These compounds are discussed together for muscle growth, sold by the same suppliers and sometimes combined. The table compares what each one is and how much human evidence exists. The route column describes how each is used in studies or on protocol websites, not tested doses.

MK-677 is the only one with randomized trials of the compound itself, and those showed more lean mass without more strength. No study has compared any of these with follistatin, so the table cannot say which works better. [141], [144], [6]

Common questions about Follistatin-344

How long does Follistatin-344 take to work?

There is no reliable answer. No study has measured what a follistatin vial does over time in people. Forum users who report a change usually describe scale-weight gains or "pumps" within the first one to two weeks, which is also when water and stored carbohydrate shift with heavy eating; others notice nothing at all. In the gene therapy trials, changes in walking distance were measured over six months to a year. [30], [31], [6] See what people reported over time.

Is Follistatin-344 a peptide or a steroid?

Neither, strictly. It is a full-sized protein of 315 amino acids once mature, far larger than the short peptides it is sold alongside, and US rules class proteins of this size as biological products. It is not a steroid: anabolic steroids are small ring-shaped molecules that act on hormone receptors, while follistatin works by capturing signal proteins outside cells. It is still banned in sport. [1], [113], [12]

Is Follistatin-344 the same as follistatin gene therapy?

No. In the human research, FS344 was a gene delivered once into muscle by a modified virus, so the muscle kept making follistatin for months or years. A vial sold as Follistatin-344 contains protein that is injected repeatedly, if it contains follistatin at all, and how long it lasts in people has never been measured. Results from gene therapy cannot be used as evidence for vials. [6], [13], [10] See the gene therapy and vial comparison.

Can epicatechin or YK-11 raise follistatin instead?

Not in a way shown to build muscle reliably. Epicatechin, a plant compound found in cocoa and tea, raised the ratio of blood follistatin to myostatin in a one-week study of six people without a comparison group, and raised blood follistatin in a small trial in Becker muscular dystrophy. In an 8-week trial in 62 older men with muscle loss, epicatechin alone improved a muscle-mass measure compared with placebo, but the biggest strength changes came when it was combined with resistance training. These studies are too small to show dependable muscle growth. YK-11 is a different kind of drug (a selective androgen receptor modulator, or SARM) whose link to follistatin comes from one study of mouse cells in a dish; it is banned in sport and FDA has warned sellers about it. [145], [146], [147], [148], [12], [149]

Can a blood test show whether Follistatin-344 is working?

Not reliably. A blood follistatin test is offered mainly for research and drug trials, and different test methods can measure different forms of follistatin, which makes results hard to compare. Levels also rise naturally, about sevenfold after long exercise, by about 155% during a three-day fast, and in pregnancy, so a higher number does not show muscle growth. No published study has measured blood follistatin before and after a vial injection. [127], [168], [150], [88], [89], [90] See what to monitor.

Why do online guides often mention 100 mcg?

Because it has been repeated for years, not because it was tested. The "100 mcg a day for 10 days" pattern uses exactly one 1 mg vial, appears in a forum log from 2011, and is repeated across many dosing pages today. No study has tested any amount of injected follistatin protein in people. [25], [3], [4] See where the numbers come from.

Is it legal to buy Follistatin-344?

It depends on where you live, but it is not an approved medicine anywhere we checked. In Australia, possessing it without authority is illegal. In the United States, FDA told a pharmacy that follistatin did not qualify for compounding, and Canada's drug database lists no follistatin product. A "research use only" label does not make a product legal or safe for human use. See the dated legal-status summary. [11], [18], [167], [116]

What is FLGR242, or "long-acting follistatin"?

It is a branded product, not a studied medicine. One seller markets FLGR242 as a modified, fragmented version of follistatin that it says does not bind activin and lasts longer in the blood. [151] A promotional blog post that credits the seller's scientists says an albumin-binding attachment gives it a 19-day half-life. The post gives 2.5 mg once a week or 5 mg every two weeks, injected subcutaneously into the belly (5 mg a week for "advanced users"), and says breaks are not needed. [170] Each of those injections is 25 to 50 times the common 100 mcg Follistatin-344 amount. We found no published study, trial registration or independent analysis showing what it contains, how long it lasts or whether it avoids activin, so the 19-day figure is a marketing claim, not a measurement. In the community education groups we reviewed, the results users described were not measured. See how to judge these accounts.

Glossary

Plain explanations of the route, dosing and research terms used in this guide. Underlined terms in the text link here.

AAV (adeno-associated virus)

A small virus that does not cause disease, modified to carry a gene into cells. The follistatin gene therapy trials used AAV to deliver the follistatin gene into muscle.

Activin

A family of signal proteins that help control fertility hormones, healing, scarring and muscle. Follistatin binds activins as well as myostatin.

Adverse event

A harmful or unwanted medical event reported after someone used a treatment. A report alone does not prove the treatment caused it.

Aggregation

Protein molecules clumping together. Tested black-market follistatin products contained a high share of clumped molecules.

Amino acid

A small chemical building block. Chains of amino acids make up peptides and proteins.

Animal study

Research in animals such as mice, rats or monkeys. It shows what a substance does in a living body, but results in people can differ.

Anti-drug antibodies

Antibodies the immune system makes against a medicine. They can weaken the medicine or cause reactions. Many patients given ACE-083 developed them.

Bioavailability

How much of a dose reaches the bloodstream in a usable form. It depends heavily on the route and has never been measured for follistatin vials in people.

Biological product (biologic)

A medicine made from living cells, such as a protein or an antibody. In the US, proteins longer than 40 amino acids, including follistatin, are regulated as biologics.

Cell study (in vitro)

Research on cells grown in a dish. It gives early clues about biology, but it is far from proof of benefit in people.

Compounding

When a pharmacy prepares a customized medicine from individual ingredients. In the US, federal lists control which bulk ingredients pharmacies may use.

Controlled trial

A study that compares people who receive a treatment with a similar group who do not, often receiving a placebo instead. Randomly assigning people to each group makes the comparison fairer.

Course and cycle

A course is the period of repeated use, such as 10 days. A cycle is a course plus a planned break before any further use.

Central serous chorioretinopathy (CSCR)

An eye condition in which fluid collects under the retina, often blurring or dimming central vision. It was reported in 11 bodybuilders after follistatin-344 injections.

Daily total

All the amounts given in one day, added together. For example, 100 mcg twice daily is a 200 mcg daily total.

Dose (amount each time)

The amount given on one occasion. A protocol lists both the dose and how often it is given.

FSH (follicle-stimulating hormone)

A hormone from the pituitary gland that drives egg development in women and sperm production in men. Follistatin was first discovered because it lowers FSH.

Freeze-dried (lyophilized)

Dried by freezing and removing the water, leaving a powder. Follistatin vials are sold this way and mixed with liquid before injection.

Gene therapy

A treatment that delivers a gene into cells so the body makes a protein itself. The follistatin gene therapy trials gave one injection into muscle; it cannot be stopped once given.

Half-life

The time it takes for the measured level of a substance in the blood to fall by half. It is not the same as how long an effect lasts.

Intramuscular (IM)

Injected into a muscle.

Intravenous (IV)

Given directly into a vein, so it enters the bloodstream immediately.

Investigational

Still being studied and not approved by a regulator, such as the FDA, to treat any condition.

Loading phase

Starting with a higher amount for a short period, then lowering it. One follistatin page uses 200 mcg a day for three days, then 100 mcg a day.

mcg and mg

Micrograms and milligrams. 1 mg equals 1,000 mcg. Follistatin vials usually hold 1 mg, and protocol amounts are written in mcg.

Myostatin

A protein made by muscle that limits muscle growth, like a built-in brake. Follistatin binds it and stops it from working.

Orphan designation

A US status that supports development of a treatment for a rare disease. It is not an approval.

Peptide

A short chain of amino acids. Follistatin, at 315 amino acids when mature, is a full-sized protein rather than a peptide.

Pharmacokinetics

How the body absorbs, moves, breaks down and removes a substance. It has not been studied for follistatin protein in people.

Placebo

A dummy treatment with no active ingredient, used as a comparison in studies.

Plasmid

A small ring of DNA that cells can read to make a protein. One company gave a follistatin plasmid as a single injection into belly fat.

Preclinical research

Studies done before research in people: cell studies and animal studies.

Reconstitution

Mixing a freeze-dried powder with a liquid so it can be measured and injected. The amount of liquid sets how much follistatin each unit holds.

Research use only

A label on products sold for laboratory research. It does not mean a product is approved, tested for human use or legal to sell as a medicine.

Satellite cells

Stem cells that sit on muscle fibers and help muscles grow and repair.

Schedule 4 (Australia)

Australia's prescription-only medicine category. Follistatin is listed there and in Appendix D, which makes possession without authority illegal.

Subcutaneous (SC)

Injected into the fatty layer just under the skin. This is the route most follistatin protocol descriptions use.

Syringe units

Markings on an insulin syringe that measure volume. On a U-100 syringe, 100 units equal 1 mL. The amount of follistatin per unit depends on how the vial was mixed.

Titration

Adjusting a dose in steps, either starting lower and increasing or starting higher and reducing.

Vector genomes (vg)

A count of virus particles carrying a gene, used to dose gene therapy. It cannot be converted into micrograms of protein.

WADA

The World Anti-Doping Agency, which publishes the list of substances banned in sport. Follistatin is on it under category S4.3.

Withdrawal and rebound

Withdrawal effects are symptoms caused by stopping a substance. A rebound is a problem returning worse than before after stopping. Neither has been studied for follistatin vials.

Supporting research: muscle, fertility and other animal studies

How this guide was researched

This guide is built from a thorough review of the sources cited throughout it: published scientific studies, registered clinical-trial plans, regulatory documents and published protocol descriptions. We also reviewed public online forums and community education groups where people describe their own experiences with Follistatin-344.

The guide cites 170 sources, including 77 original scientific papers. Each type of source answers a different question. Studies show what researchers measured. Protocol descriptions show how Follistatin-344 is typically used. Personal accounts show what individual people experienced. Every numbered citation links to its entry below, labeled by source type.

How this guide was made

Research and drafting were AI-assisted. Every cited source was checked against the original, and the guide was reviewed and edited by Doserly before publication. It has not had an independent clinical review, and Doserly does not currently have medical reviewers. Doserly makes a medication and health-tracking app and runs Doserly Academy, both of which are promoted in this guide. Read our editorial policy for how guides are researched, updated and corrected.

This guide is for educational purposes. It summarizes what the reviewed sources report so the research is easier to understand; it is not medical advice. For a deeper dive, or to check any point for yourself, go straight to the cited sources.

Explore the sources