How to Inject Testosterone: The Definitive Guide

What does injecting testosterone involve?

Most injectable testosterone is an ester, testosterone with a small chemical tail, dissolved in oil. Injected into a muscle, the oil forms a small pool called a depot, and the testosterone seeps out of it slowly. That is why injections are given weekly or every few weeks rather than every day. [1], [2]

There are two routes. Intramuscular injection (IM, into a muscle) is the route on almost every label. Subcutaneous injection (SC, into the fatty layer under the skin) is labeled in the US only for Xyosted, a prefilled autoinjector; using a cypionate or enanthate vial subcutaneously is off-label (outside the approved label), although a UK guideline accepts it for weekly doses. [2], [4], [5]

Who injects depends on the product: Aveed only in certified healthcare settings, Sustanon 250 and Testosterone Enantate by a doctor or nurse, and Nebido by a doctor (UK leaflets), and Xyosted by you after training. US vial labels do not say. Checked September 2026. [7], [14], [15], [16], [4]

How much to inject is your prescriber's decision and is covered in the TRT dosage guide; hands-on technique is best learned in person from a nurse, pharmacist or prescriber.

Injecting testosterone: the key numbers

This table shows what each product label and clinical guideline says about where and how testosterone is injected, and who gives it. The labels come first because they are the approved instructions. Checked September 2026.

[2], [1], [3], [4], [7], [8], [15], [17], [14], [18], [19], [16], [20], [21], [5], [22], [23], [6], [24], [25], [26]

US vial labels name only the buttock muscle; UK and Canadian guidelines also list the thigh; only Xyosted is labeled for subcutaneous injection; and every oil label that gives a speed asks for a slow injection. No randomized trial has compared injection sites for testosterone: one 1995 study compared pain and bleeding by site, not testosterone levels (see which site hurts less). Labels describe the sites used in the studies behind each approval; the Australian undecanoate label calls the buttock "the only site for which clinical experience has been obtained". Guidelines add sites and routes used in practice. [27], [5], [6]

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Where testosterone injections go, by source

Sites named in product labels, clinical guidelines and patient leaflets (checked September 2026).

Teal markers: intramuscular (into a muscle). Gold marker: subcutaneous (into the fat layer). The dashed ring marks the area around the navel to avoid.

1. Buttock (gluteal muscle) · intramuscular

Labels: US vial labels (Depo-Testosterone, generic cypionate and enanthate, Azmiro), Aveed (upper outer part), Nebido (UK), Canadian monographs; Reandron (Australia): the only site with clinical experience

Guidelines: Society for Endocrinology (UK), Canadian Urological Association (CUA)

Leaflet: Sustanon 250 (UK)

2. Thigh · intramuscular

Guidelines: Society for Endocrinology (upper thigh), CUA (thigh)

Leaflet: Sustanon 250 (upper leg)

3. Upper arm (deltoid) · intramuscular

Leaflet: Sustanon 250 (upper arm)

Study: one 1995 study of nurse-given weekly injections

4. Abdomen (belly) · subcutaneous

Label: Xyosted (US) only, not within 2 inches (5 cm) of the navel

No randomized trial has compared injection sites for testosterone. The side-of-the-hip (ventrogluteal) site is not named on any testosterone label.

How do milligrams, millilitres and syringe units fit together?

Syringe units measure volume, not testosterone. On a U-100 insulin syringe, 100 units equal 1 mL, so 1 unit is 0.01 mL. [11] To turn a dose into a volume, divide the dose by the vial's strength:

• 100 mg from a 200 mg/mL vial is 0.5 mL, or 50 units.
• 100 mg from a 100 mg/mL vial is 1 mL, or 100 units: twice the volume for the same dose. US cypionate comes in both strengths. [2]
• A split dose. If a prescriber splits 100 mg a week into two injections, each is 50 mg: 0.25 mL, or 25 units, at 200 mg/mL.

Mixing up milligrams, millilitres and units causes real errors: the US Food and Drug Administration (FDA) has reported patients drawing 50 units instead of 5 of a different injectable medicine. [28] The TRT dose calculator shows each step for your vial's strength, and the TRT dosage guide covers the doses themselves.

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Milligrams, millilitres and syringe units

A 1 mL U-100 syringe: 100 units = 1 mL, so 1 unit = 0.01 mL. Units measure volume, not testosterone.

A. 100 mg from a 200 mg/mL vial

100 mg ÷ 200 mg/mL = 0.5 mL = 50 units

B. Split dose: 50 mg from a 200 mg/mL vial

50 mg ÷ 200 mg/mL = 0.25 mL = 25 units

100 mg from a 100 mg/mL vial = 1 mL = 100 units: the whole syringe. The TRT dose calculator shows each step.

How does an injected oil depot work?

The oil slows everything down: the US enanthate label says esters in oil "are absorbed slowly from the lipid phase", so doses can be weeks apart. The body then removes the ester tail to free testosterone. [1]

How long a depot lasts depends mostly on the ester, not the route:

• Cypionate. The US label gives a half-life of about 8 days after intramuscular injection. [2]
• Enanthate. The UK label gives a blood half-life of 2 to 3 days in healthy men. The two figures were measured in different ways, so they are not a head-to-head comparison. [18]
• Time to peak. Median 71.7 hours (about 3 days) after 200 mg of intramuscular Azmiro, 11.9 hours for weekly subcutaneous Xyosted and 7 days for intramuscular Aveed. Different products and doses, so this does not show that one route is faster. [3], [4], [7]

Small studies that gave the same product both ways found similar overall exposure: with undecanoate, levels peaked later after subcutaneous injection (8.0 vs 3.3 days) but reached similar levels, and in 14 transgender men the total amount of testosterone in the blood per milligram injected was similar by route. [31], [32] The testosterone level visualizer shows how injection frequency changes the peaks and troughs.

What is in the vial, and does the oil matter?

The oil differs by product, which matters if you have an allergy:

[2], [29], [33], [1], [4], [16], [15], [34], [17]

A vial can look cloudy if a wet needle or syringe was used; the US enanthate label says this does not affect potency. [1] Crystals are covered under storage.

Does cypionate or enanthate change how you inject?

Not on the US labels, which use the same buttock site and dose range for both. They differ in oil and ester, and injectable products are not substitutable milligram for milligram, so a switch is a prescriber's decision. See cypionate vs enanthate. [2], [1], [3]

What does the research show?

The research is thin: small studies comparing routes, product trials that counted local reactions, a few studies of the oil cough, and imaging studies of needle length done for vaccines and other medicines. [35], [9]

Is subcutaneous injection as good as intramuscular?

For blood levels, small studies suggest yes; for long-term safety, nobody knows. No randomized trial has compared the same cypionate or enanthate vial given subcutaneously and intramuscularly in men with hypogonadism.

• Guidelines split. The UK Society for Endocrinology says weekly subcutaneous cypionate or enanthate at 50–100 mg is comparable and supports self-management. The BSSM agrees for enanthate but notes no long-term studies of subcutaneous "micro-dosing" and little long-term data for cypionate. The VA keeps subcutaneous testosterone for specific cases only. [5], [22], [26]
• The largest comparison in men. In 234 men with hypogonadism, weekly intramuscular cypionate 100 mg and a weekly subcutaneous enanthate autoinjector 100 mg raised trough testosterone to similar levels: from 313.6 to 536.4 ng/dL (10.9 to 18.6 nmol/L) on cypionate and from 246.6 to 552.8 ng/dL (8.6 to 19.2 nmol/L) on the autoinjector. The autoinjector group had lower estradiol and hematocrit. But the ester, the device and the route all differed, and the men were not randomized, so the study cannot isolate the route. [36]
• Transgender men. In 63 transgender men on weekly subcutaneous cypionate or enanthate, all reached male-range levels, 9 had minor local reactions (4 of them small lumps that cleared in 1 to 2 days, and one a single skin infection that cleared without treatment), and all 22 who had used muscle injections before preferred subcutaneous ones (20 of them markedly). In 14 transgender men, subcutaneous injections scored lower for anxiety before injecting, pain during it and pain afterwards. [37], [32]
• A larger volume. With 4 mL of undecanoate, the picture reversed: subcutaneous injection hurt more 24 hours later, and 11 of 20 people preferred intramuscular, 6 subcutaneous and 3 had no preference. [31]

A 2022 review concluded that, with training, people can self-inject subcutaneously with less discomfort, but that data are limited and direct safety comparisons are still needed. [35] What people report after switching is mixed (community reports).

How often do injections hurt, bleed or bruise?

Often a little, rarely badly. The studies below measured different things in different products, so compare within each row, not across rows.

[10], [38], [4], [39], [3], [33], [7]

In the undecanoate study, pain was worse in men whose earlier injection had hurt, and milder in older and heavier men; which experienced nurse gave the injection made little difference. [38] The US labels for cypionate list inflammation and pain at the injection site among side effects. [2]

Which site hurts less?

For testosterone, the only site comparison is one 1995 study: in 551 weekly enanthate injections, the buttock caused fewer complaints and less bleeding than the shoulder or thigh, but more often caused pain. [10]

Studies of other intramuscular medicines add detail. A 2023 review of 17 studies (1,429 people) found injections into the side of the hip (ventrogluteal) moderately less painful than the classic upper-outer-buttock site (dorsogluteal), with less bleeding and bruising and no more accidental subcutaneous injections. [40] Pressing on the injection site also reduced pain in small studies, though the studies varied a lot. [41]

Does the needle reach the muscle?

It depends on the site and the person. These imaging studies were done for vaccines and other medicines, not testosterone, and they model where a needle would reach rather than watching real injections:

• Buttock. In CT scans of 150 men, the fat over the buttock muscle averaged 23.1 mm. A 37 mm needle would have missed the muscle in 21 of 150 men (14%) and in 81 of 148 women (54.7%). [9]
• Side of the hip. In an ultrasound study, 92% of men would have received a true intramuscular injection at the side-of-the-hip site located one standard way. [42]
• Upper arm. In PET/CT scans, a 1-inch (25 mm) needle was expected to reach the shoulder muscle in 207 of 210 men under 260 lb (118 kg), or 98.6%. A 1.5-inch (38 mm) needle was expected to reach it in 6 of only 8 men over 260 lb, so that figure is very uncertain. [43]

For small watery vaccines, the US Centers for Disease Control and Prevention (CDC) uses 1 to 1.5 inch (25–38 mm) needles for intramuscular shots in men of 70–118 kg (about 154–260 lb); oil depots are thicker and larger, so this is context, not a testosterone instruction. [44] No study has measured what happens to testosterone levels when an intended intramuscular injection lands in fat.

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Does the needle reach the muscle? Three imaging studies

Each card is a separate study with its own measure, so the bars are not on one shared scale.

Buttock (CT scans, 150 men)

A 37 mm needle would miss the muscle in 14% of men (21 of 150)

Women: 54.7% (81 of 148)

Average fat over the muscle in men: 23.1 mm

Side of the hip (Ultrasound, 28 men)

92% of men would get a true intramuscular injection at the site located one standard way

The study does not say which needle length was assumed

Upper arm (PET/CT scans, 218 men)

A 1-inch (25 mm) needle reaches the shoulder muscle in 98.6% of men under 260 lb (207 of 210)

Over 260 lb, a 1.5-inch (38 mm) needle: 6 of only 8 men

Modelled needle reach from studies of vaccines and other medicines, not testosterone injections.

Is injecting testosterone safe?

Usually, when it is done as the label describes. Most problems are minor pain, bleeding or bruising at the site. Serious local problems such as infection or nerve injury appear mainly as case reports, and the serious reaction that labels warn about, oil reaching the lungs, is best known with long-acting undecanoate. [10], [4], [45], [46], [7] This section covers the injection itself; the effects of testosterone on red blood cells, the heart and fertility are in the TRT side effects guide.

Why do some people cough right after an injection?

A sudden cough during or just after an oil injection is usually put down to pulmonary oil microembolism (POME): tiny droplets of the oil reaching the lungs. Labels list an urge to cough, coughing fits, shortness of breath, throat tightening, chest pain, dizziness and fainting. Most episodes on the Aveed label lasted a few minutes, but some lasted hours and needed emergency care. [7], [1]

How often it happens depends on the product and on how carefully people look:

[7], [8], [47], [48], [10], [49]

Watching every injection finds far more mild episodes than waiting for reports, which is why the rates differ so much. The Endocrine Society says the cough is reported even more rarely after enanthate and cypionate than after undecanoate. [24], [1]

Labels respond with slow injection, watching the person during and after it and, for Aveed, 30 minutes in the clinic. The BSSM says the risk is lower if the injection takes several minutes, and in the Aveed safety review, technique or dosing problems were a possible factor in 3 of 4 cases that reached emergency care. [7], [15], [22], [48]

Chest pain, trouble breathing or fainting after an injection needs urgent medical help, and the prescriber should hear about any episode, because repeat episodes in the same men were more common than chance in the Australian series. [7], [47] A blood clot in the lung is a different problem, listed separately on the labels. [3]

Are lumps, bruises and bleeding normal?

A little bleeding or bruising is. The Xyosted instructions say slight bleeding after an injection is normal: hold a cotton ball or gauze on the spot for a few seconds and do not rub. The VA notes possible bruising and redness with intramuscular injections. [4], [26]

Small lumps after subcutaneous shots come up often in community reports. In one study of 63 transgender men on prescribed weekly subcutaneous testosterone, 4 reported small lumps that cleared in 1 to 2 days; no study has counted them in men on TRT. [37] Rarely, oil that stays in tissue forms an oil granuloma (a firm, walled-off lump): one case report describes painful lumps in both shoulders and a buttock found 9 years after a bodybuilder's non-prescribed oil injections. [50]

Can an injection get infected?

Yes, though no study has measured how often in men on TRT. In the study of 63 transgender men on subcutaneous injections, one had a single skin infection (cellulitis) that cleared without treatment. [37] A 2026 case report describes a 72-year-old man who developed a persistent thigh abscess (a pocket of pus) after a routine testosterone injection. It was caused by an unusual bacterium and needed surgical drainage and prolonged specialist antibiotics; his hospital stay was also complicated by breathing failure that needed intensive care. [45]

Guidance lowers the risk: a new sterile needle and syringe every time, and only healthy skin, not skin that is tender, bruised, red, hard or scarred. [51], [52], [4] A lump that keeps growing, feels hot, turns red, becomes more painful after the first day or two, or comes with a fever needs a clinician promptly.

Can you hit a nerve or a blood vessel?

It is possible, which is why labels describe the site so exactly. The Aveed label says to use the upper outer part of the buttock and avoid the superior gluteal arteries and the sciatic nerve, the large nerve running down the back of the leg. A review of injection injuries found that sciatic nerve damage from buttock injections is avoidable but still happens worldwide; most reported cases were in children, and the review covered injections in general, not testosterone. [7], [46] The US labels also say to avoid injecting into a vein, and cypionate is "not for intravenous use". [1], [2]

Who should be especially cautious?

• Men with a bleeding disorder, low platelets, or on blood thinners. The Endocrine Society of Australia says deep intramuscular undecanoate is unsuitable with bleeding disorders or low platelets. In one clinic, 269 undecanoate injections in men on blood thinners caused no bleeding lump. US labels note that testosterone can increase the effect of warfarin-type blood thinners. [25], [47], [2]
• People with oil or ingredient allergies. Sustanon 250 is not for people allergic to peanut or soya, and Xyosted is not for people allergic to sesame oil. [17], [4]
• Anyone who has had a cough or breathing reaction after an injection, and very lean or heavier men, whose needle reach differs (the research). [47], [9]
• People with diabetes. US labels say testosterone may lower blood sugar and insulin needs. [2]
• Drug-tested athletes. Testosterone is prohibited in sport at all times. [13]
• Under-18s. Testosterone for teenagers belongs only in specialist care.
• Women. This guide is written for men. Testosterone for women uses different doses and products; see testosterone therapy for women.

Can testosterone be mixed with other injections?

No testosterone label describes mixing it with another medicine in one syringe; UK labels say to inject the oil immediately after drawing it up. [18], [8] Ask a pharmacist first. hCG, which some men use alongside testosterone, is covered in the hCG guide. Checked September 2026.

Is testosterone legal, and is it allowed in sport?

Checked September 2026. Rules differ by country and change often.

• United States. Testosterone and its esters are Schedule III controlled substances, prescription only. No proposal to change that has been published. [12]
• United Kingdom. Testosterone is a Class C controlled drug. [53]
• Canada. Testosterone is a Schedule IV controlled substance. [54]
• Australia. Testosterone is a Schedule 4 prescription-only medicine. [55]
• Sport. The World Anti-Doping Agency (WADA) prohibits testosterone at all times, and its 2027 list, published in September 2026, keeps the ban. [13], [56]

What do labels and guidelines say about technique?

The labels describe the same basic steps: check the liquid, use a new sterile needle and syringe, inject slowly into the named site, rotate sides and put used sharps straight into a proper container. This is a summary, not a substitute for being shown in person. [2], [7], [4]

[2], [16], [1], [8], [51], [52], [7], [3], [4], [18], [57]

Should you pull back on the plunger before injecting?

The sources disagree, and the answer depends on the product. The Aveed label tells clinicians to aspirate (pull back on the plunger) for several seconds and to start again with a fresh dose if blood appears. [7] A 2025 review of 6 randomized trials (693 people, mostly children and vaccines) found that aspirating made injections more painful and slower, with no serious complications reported when it was skipped; its authors said the technique should depend on the type of medicine. CDC vaccine guidance also notes that aspiration can increase pain. [58], [44] For Aveed, the label applies. Other testosterone labels do not mention aspiration, so ask the nurse or pharmacist who trains you.

Do warming the oil, changing the needle or pressing on the skin help?

Pressing on the site may help. In small studies of other intramuscular medicines, pressing on the injection site reduced pain, though the results varied a lot and some studies were biased; warming the liquid did not help, a fresh needle after drawing up gave conflicting results, and there was not enough evidence for the "Z-track" technique (pulling the skin sideways first). Labels mention warming only to redissolve crystals. [2], [41] Aveed's label gives the reason for its separate 18-gauge drawing needle: it makes drawing the medicine out of the vial easier. [7]

How should you rotate injection sites?

Change sites so the same spot is not used again and again. Aveed alternates left and right buttock; Xyosted allows either side of the abdomen, away from the navel and any damaged skin. [7], [4] In the weekly enanthate study, the side of the body made no difference to side effects. [10] A simple record of date, site, side and any reaction shows which spots were used last and which cause trouble.

Sites, needles, syringes and supplies: practical questions

Where can you inject testosterone: buttock, thigh, shoulder or belly?

It depends on the product. US vial labels name only the buttock muscle; the UK Society for Endocrinology adds the upper thigh, the CUA the thigh, and the UK Sustanon leaflet the upper arm. The only belly site on a label is Xyosted's, given subcutaneously. [2], [7], [5], [6], [14], [4]

The shoulder (deltoid) appears in the old nurse-given enanthate study, not on US labels. The side of the hip (ventrogluteal) is not named on any testosterone label, but studies of other medicines found it less painful than the classic buttock site. [10], [40] If you want to use a site your label does not name, agree it with your prescriber first.

What needle size is used for testosterone injections?

The labels cited here give no needle size for the injection itself. Aveed names only the 18-gauge needle used to draw the oil up, and the Azmiro prefilled syringe comes without a needle ("obtain suitable needle separately"). [7], [3] Outside the labels, a UK administration guide for long-acting undecanoate, approved by the UK medicines regulator, suggests a 20-, 21- or 22-gauge needle chosen for the person's fat and muscle. [59] Needles are described by gauge, where a higher number means a thinner needle, and by length.

The length that reaches muscle depends on the site and the person (needle reach), so your prescriber or pharmacist supplies needles for your product, site and build. [9], [43]

Can you use an insulin syringe for testosterone?

For measuring volume, the arithmetic works: a U-100 insulin syringe is marked in units, with 1 mL shown as 100 units and 0.5 mL as 50 units. [11] The practical limits are the oil and the needle: in community reports, very fine insulin-syringe needles drew thick oil slowly, while others used them for subcutaneous or shoulder injections. Whether one suits your product and route is a question for your prescriber or pharmacist. See how the units work.

Can you pre-fill syringes ahead of time?

No label or official source gives a safe time for testosterone drawn into ordinary syringes ahead of use. The UK enanthate and Nebido labels say to inject immediately after drawing up, and the CDC advises preparing injections as close as possible to the time they are given. [18], [8], [51] Some people report oil appearing to soak into the rubber plunger of pre-filled syringes, but that is an observation, not a study (community reports).

How should testosterone be stored, and why can crystals form?

It depends on the product. The US cypionate and enanthate vials are kept at room temperature, and cypionate also away from light; UK Nebido has no special storage conditions. Cypionate and enanthate can form crystals when they get colder than the labeled range; warming and shaking or rolling the vial should redissolve them. [2], [1] The leaflet in your box is the final word for your product.

[2], [29], [1], [3], [4], [7], [17], [8]

How long does an opened vial last?

The US Depo-Testosterone and generic enanthate labels cited here give no in-use period for an opened multi-dose vial, so follow the instructions for the vial you receive. US guidance for healthcare settings says to date an opened multi-dose vial and discard it within 28 days unless the manufacturer states another date; Canadian cypionate monographs say to discard it 56 days after first use. The printed expiry date applies to an unopened vial. [51], [20], [21] The testosterone cypionate guide covers storage in more detail.

Blood came out after the injection. Did I lose my dose?

Probably not much, though no study has measured it. The Xyosted instructions treat slight bleeding as normal. [4] Doses can also be lost through the device or technique: in a usability study of a Xyosted-type autoinjector, done with observers watching, 99 of 123 attempted injections (80.5%) delivered a full dose, and the most common error was not holding it against the skin long enough (at least 8 seconds). [60] That is why the Xyosted instructions say to hold it down for a full 10 seconds. [4]

How do you get rid of used needles?

Put each used needle and syringe straight into a sharps container; never put loose needles in household trash or recycling, and never flush them. [57]

• United States. Use an FDA-cleared sharps container or a heavy-duty plastic household container with a tight, puncture-resistant lid, such as a laundry detergent bottle. When it is about three-quarters full, follow local rules: drop-off sites, mail-back programs or special pick-up. [57], [61], [4]
• United Kingdom. Dispose of the needle and syringe together as one unit, do not fill the bin above its fill line, and do not use drink cans or bottles. [52]
• Canada. The cypionate monographs say to put used needles and syringes straight into a designated safety box or puncture-proof container. [20]
• Australia. NSW Health advises a puncture-proof container taken to a public sharps bin or a participating pharmacy, medical centre or hospital. [62]

Can you travel with injectable testosterone?

Yes, with preparation. In the US, the Transportation Security Administration allows unused syringes when they are carried with injectable medication, and used ones must go in a sharps or hard-sided container. Rules for controlled medicines differ by country. See traveling with testosterone. Checked September 2026. [63]

What if needles make you anxious?

There are options to discuss. In 14 transgender men, subcutaneous injections caused less anxiety beforehand than intramuscular ones; Xyosted is an autoinjector made for self-injection after training; and clinic-given injections remain an option (for Aveed and several UK products, the only one). [32], [4], [7], [14]

What do people report about injecting testosterone?

Public forums are full of men comparing sites, needles and routes, and asking whether a lump or a sore spot is normal. The accounts below come from public Reddit threads posted between September 2025 and September 2026, read with their replies. They show what people experience, not how often it happens, and several involve products that did not come from a pharmacy.

What happens when people switch from intramuscular to subcutaneous?

Results point both ways, and most switches changed something else too. One man moved to 30 mg of subcutaneous enanthate in the belly every other day and, two weeks later, described better sleep, erections and energy, with no lumps. [64] Another found injections easier after moving from weekly muscle shots to twice-weekly subcutaneous shots at the same 100 mg a week, but his mood, libido and erections got worse. [65]

Lab results rarely isolate the route. One man's testosterone fell after the switch, but his dose had also dropped. [66] Another recorded 1,151 ng/dL (about 40 nmol/L) on every-other-day muscle shots and 667 ng/dL (about 23 nmol/L) on daily subcutaneous shots, while his hCG timing, syringes, weight and sleep apnea treatment also changed. [67] Hematocrit fell for one man after he moved to three belly injections a week, alongside about 25 lb of weight loss. Another man started daily subcutaneous shots to bring his hematocrit down; about nine weeks later it was 57.4%. [68], [69]

What do people say about lumps, pain and the oil?

Lumps after subcutaneous shots come up often in these accounts. One man's red, itchy lumps began in his sixth week of twice-weekly shots and lasted longer each time, until he moved back to muscle; another had lumps lasting about a week whatever the needle size; others describe small lumps that clear within hours. [70], [71], [72]

Several stories blame the oil or a new vial. Itchy skin from subcutaneous cypionate in grapeseed oil settled for one man after he switched to muscle injections at the side of the hip; large lumps from a non-pharmacy product in MCT oil eased with an antihistamine and did not return with a different product. [73], [74] Pain after buttock injections from a new 400 mg/mL enanthate vial was easing by day eight, and severe thigh pain from a new non-pharmacy supply did not recur. [75], [76] None of these accounts can show what caused the reaction.

Which sites and needles do people find easier?

Preferences differ widely. One man found a 27-gauge, 13 mm needle in the shoulder painless after nine months of 25-gauge, 25 mm needles in the buttock or leg; another's first warmed shoulder injection was painless after weeks of uncomfortable belly shots. [77], [78] Others went the opposite way, feeling best on deeper thigh and buttock injections with 1-inch and 1.5-inch needles. [79] A wife describes her husband's first self-injection, low on the thigh near the knee, followed by two weeks of swelling and difficulty walking. [80]

What goes wrong with needles, syringes and volumes?

• Oil through fine needles. A 31-gauge insulin syringe drew the oil too slowly for one man; another found a 0.5 mL shoulder injection through a 27-gauge needle on a 3 mL syringe hard to push, ending in bleeding. [81], [82]
• One needle for everything. Drawing up and injecting with the same small needle left one man struggling to pierce the skin; later injections with a fresh 27-gauge insulin syringe caused no pain. [83]
• Where the dose went. Men ask whether a half-inch needle at the side of the hip reaches muscle, and one found that a pen dripping after removal may have delivered incomplete doses for two weeks. [84], [85]
• Units and millilitres. Replies pointed out that one man's 0.12 mL a day from a 200 mg/mL vial was 24 mg a day, about twice the weekly dose he thought he was taking. [86]
• Pre-filled syringes. Pre-filled insulin syringes of an MCT-oil product appeared to lose volume within hours as the plunger seal swelled. [87]

When do people get reactions checked, and what about needle fear?

The threads that drew the most urgent replies involved warmth, spreading swelling or a growing lump: warm, itchy thigh swelling after a reused needle, and a prominent bulge after alternating between only two sites. [88], [89] Fear of needles often eases: one man was frightened by the large drawing needle before his first belly injection, which turned out to be easy with a smaller needle, while another found one-inch needles so distressing that he tried inserting them only partway. [90], [91]

How can you judge an injection story?

Ask: Was the product from a pharmacy, and in which oil and strength? Was it injected into muscle or fat, where, and with what needle? Was the dose written in milligrams, not just units? What else changed at the same time? When was blood drawn relative to the last injection? And what happened over the following months?

These selected discussions show what people experience and the questions research has not answered. They are not a survey of all men who inject testosterone, a success rate or a substitute for the studies above.

What should you track?

The site and side of each injection, and any reaction, alongside the blood tests your prescriber orders. Use this summary to prepare questions for your prescriber; it is not a personal plan.

[7], [4], [2], [47], [23], [92]

The TRT blood work guide explains when to draw each test, and the hematocrit guide covers the red-cell numbers. Noting the date of any change of route, site or needle makes later results easier to read.

Common questions about injecting testosterone

Is it better to inject testosterone in the glute, the thigh or the shoulder?

US vial labels name only the buttock (glute) muscle; UK and Canadian guidelines add the thigh, and the UK Sustanon leaflet the upper arm. No randomized trial has compared sites, so none has been shown to work better. [2], [5], [6], [14], [10] See the key numbers.

Can you inject testosterone subcutaneously instead of intramuscularly?

Only Xyosted is labeled for it in the US; using a vial subcutaneously is off-label. A UK guideline accepts weekly subcutaneous doses of 50–100 mg, and small studies found similar blood levels. One small randomized crossover study compared the two routes for undecanoate in 20 people, 11 of them men with hypogonadism; no randomized trial has compared them for a cypionate or enanthate vial in these men. Discuss any change with your prescriber. [4], [5], [37], [35], [31] See the research.

What size needle do you use for testosterone?

The labels cited here give none for the injection itself, though a UK administration guide for undecanoate suggests 20 to 22 gauge. The length needed depends on the site and body fat: a 37 mm needle would miss the buttock muscle in about 1 in 7 men. Your prescriber or pharmacist supplies suitable needles. [7], [59], [9] See needle size.

How many units is 100 mg of testosterone?

At 200 mg/mL, 100 mg is 0.5 mL, or 50 units on a U-100 insulin syringe. At 100 mg/mL, it is 1 mL, or 100 units. Units measure volume, so the answer depends on your vial's strength. [11], [2] The TRT dose calculator shows each step. See how the units work.

Are testosterone injections painful?

Usually only mildly. In 551 nurse-given weekly injections, 70.6% caused no complaint, and in the Xyosted 52-week study more than 95% of men reported no injection-related pain. Large undecanoate injections hurt more often, for 1–2 days. [10], [93], [38] See how often injections hurt.

Is there a risk of oil embolism from testosterone injections?

Yes, but serious episodes are rare. It is best known with long-acting undecanoate, and the Endocrine Society says it is reported even more rarely after enanthate and cypionate. A sudden cough or breathlessness during or just after an injection can mean oil reached the lungs; most episodes pass within minutes, but chest pain, trouble breathing or fainting needs urgent help. [7], [24], [22] See the cough after an injection.

Do injections raise hematocrit more than other forms?

Not clearly, except compared with patches. In a combined analysis of 29 placebo-controlled trials, cypionate or enanthate injections raised hematocrit by about 4.0 points, against 3.0 for gels and 1.4 for patches. Oral undecanoate capsules raised it by 4.3 points and long-acting undecanoate injections by 1.6. Only the difference from patches was clear; the other differences could have been chance. Whether the injection route matters is unsettled. [92], [36] The hematocrit guide has the full picture.

Glossary

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

Anaphylaxis

A severe, whole-body allergic reaction that can affect breathing and blood pressure. It needs emergency treatment.

Aspiration

Pulling back on the plunger after the needle is in, to check that no blood comes into the syringe. The Aveed label asks for it; vaccine guidance does not.

Autoinjector

A prefilled, spring-loaded device that inserts the needle and delivers a set dose when pressed against the skin. Xyosted is one.

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.

Depot

A pool of medicine left in the body, such as oil in a muscle, that releases the drug slowly over days or weeks.

Dorsogluteal site

The classic injection site in the upper outer part of the buttock. The Aveed label uses this area (the gluteus medius muscle).

Ester

A chemical tail joined to testosterone that makes it dissolve in oil and release slowly after injection. The body removes the tail to free testosterone. Cypionate, enanthate and undecanoate are esters.

Estradiol

The main form of estrogen. In men it is made mostly from testosterone, so it rises when testosterone rises.

Needle gauge

A number describing how thick a needle is. A higher gauge means a thinner needle: a 27-gauge needle is thinner than an 18-gauge one.

Gluteal

Of the buttock muscles. US testosterone vial labels say to inject deep into the gluteal muscle.

Half-life

The time it takes for the level of a substance in the blood to fall by half. For injected testosterone esters it mostly reflects how slowly the oil depot releases the drug.

Hematocrit

The share of the blood made up of red blood cells. Testosterone raises it, which is why it is checked on treatment.

Intramuscular (IM)

Injected into a muscle. Most testosterone cypionate and enanthate is given this way.

Product label (prescribing information)

The official document approved by a medicines regulator for a product, describing its approved uses, doses, how to give it and warnings. In the UK it is called the summary of product characteristics.

Meta-analysis and systematic review

A systematic review gathers all studies on a question in a planned way. A meta-analysis combines their results statistically.

Off-label

Used in a way the product label does not describe, such as a different route or site. Prescribers may do this, but the label's studies do not cover it.

Oil granuloma (oleoma)

A firm lump that forms when the body walls off injected oil that stays in the tissue. It is rare and can appear long after the injections.

Pharmacokinetics

How the body absorbs, moves, breaks down and removes a substance.

Placebo

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

Pulmonary oil microembolism (POME)

Tiny droplets of injected oil reaching the lungs, causing a sudden cough, breathlessness or dizziness during or soon after an injection. It is rare, and best known with long-acting undecanoate.

Sharps container

A puncture-resistant container with a tight lid for used needles and syringes. Pharmacies sell approved ones; some sturdy household containers can stand in.

Subcutaneous (SC)

Injected into the fatty layer just under the skin. Xyosted is labeled this way; using a testosterone vial under the skin is off-label.

Syringe units

Markings on an insulin syringe that measure volume. On a U-100 syringe, 100 units equal 1 mL, so 0.5 mL is 50 units.

Trough level

The lowest level of a drug in the blood, measured just before the next dose.

TRT (testosterone replacement therapy)

Prescribed testosterone, by injection, gel or other forms, for men with low testosterone.

U-100 syringe

An insulin syringe marked for insulin at 100 units per mL. Its markings can be read as volume: each unit is 0.01 mL.

Ventrogluteal site

An injection site on the side of the hip, into the gluteus medius and minimus muscles. Studies of other medicines found it less painful than the classic buttock site.

WADA

The World Anti-Doping Agency, which publishes the list of substances banned in sport. Testosterone is prohibited at all times.

How this guide was researched

This guide is built from a thorough review of the sources cited throughout it: product labels and patient leaflets from the US, UK, Canada and Australia, clinical guidelines, published studies, and official guidance on injection safety and sharps disposal. We also reviewed public online forums where men describe their own experiences of injecting testosterone.

The guide cites 93 sources, including 17 studies in people, 17 product labels and patient leaflets, 7 clinical guidelines and position statements, and 28 public community discussions. Each type of source answers a different question. Labels and guidelines show what clinicians are told to do. Studies show what was measured. 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