Free TRT tool

Testosterone level visualizer

Injected testosterone is released slowly from the spot where it was injected. Choose an ester (the chemical form that sets how fast testosterone is released), a weekly amount and a schedule to see how levels rise and fall in a simple model.

Choose what to show

Ester

The ester is the part attached to testosterone that sets how fast it leaves the injection spot. It is printed on the vial label.

CypionateOil injection. Model values come from injections into a muscle.EnanthateOil injection. Model values come from injections into a muscle.PropionateA short ester that is released quicklyUndecanoateA long-acting injection into a muscle, given by a health care professionalSustanon 250A blend of four esters in one vial

Weekly amount

The total mg of the ester over one week. The chart is drawn against the long-run average, so its shape stays the same for every amount.

Injection schedule

How often the weekly amount is injected.

Compare with another schedule

Adds a dashed line for a second schedule. Each line is drawn against its own long-run average, so the shapes can be compared.

The starting values are examples so the chart has something to show. They are not a suggestion.

Estimated relative level

Estimated relative testosterone level: Cypionate, Once a week

The only study that compared cypionate and enanthate head to head found nearly identical blood levels after each (a small 1980 study in 6 healthy men, as reported in Health Canada product monographs). So this tool draws both esters with the same curve.

Level compared with the long-run average (1 = average)

Weeks since the first injection

Selected schedule (Once a week)
Long-run average
Injection
Trough: the low point just before the next injection

Estimated relative level for Cypionate, Once a week: highest and lowest value in each period (1 = long-run average)
Period	Highest	Lowest	Injections
Week 1	0.47	0.00	1
Week 2	0.76	0.37	1
Week 3	0.92	0.57	1
Week 4	1.02	0.68	1
Week 5	1.07	0.74	1
Week 6	1.09	0.77	1
Week 7	1.11	0.79	1
Week 8	1.12	0.80	1

Once levels settle

After a few injections, the rise and fall repeats the same way each time. These numbers describe that repeating pattern in this model.

Highest level (peak): 1.13 × average
Lowest level (trough): 0.81 × average
Peak-to-trough ratio: 1.39 to 1
Amount per injection: 100 mg
Time to settle (within 10%): About 4 weeks

In this model, a larger weekly amount raises the whole curve by the same factor, so the shape and the ratio do not change. That is why the chart is drawn against the long-run average instead of in ng/dL.

Peak-to-trough ratio by schedule

The peak-to-trough ratio is the highest level divided by the lowest level once levels settle. A ratio near 1 means a flatter line between injections.

Cypionate: highest and lowest level once settled, for each schedule (1 = long-run average)
Schedule	Peak	Trough	Peak-to-trough ratio
Every 2 weeks	1.39	0.57	2.43 to 1
Once a weekIn the chart	1.13	0.81	1.39 to 1
Twice a week (every 3.5 days)	1.04	0.93	1.11 to 1
3 times a week (Monday, Wednesday, Friday)	1.04	0.95	1.09 to 1
Every other day	1.01	0.98	1.04 to 1
Every day	1.00	0.99	1.01 to 1

A flatter or a wavier line is not better or safer in itself. Studies measure real levels that swing more than this model shows. The schedule that fits you is a decision for you and your prescriber.

How the model works

Each injection forms a depot
A depot is the pool of oil left where the needle went in. Testosterone leaves it a little at a time. In the blood, testosterone itself is cleared within about 10 to 100 minutes, so the slow fall after an injection comes from the depot, not from the blood.
One curve per injection
Each injection gives a curve that rises to a peak and then falls by half every half-life. The half-life and the time to the peak for each ester come from product labels and studies, listed in the sources below.
Injections add up
The model adds the curves of every injection together. After a few injections, the rise and fall repeats in the same way. This is called steady state.
Shown against the average
The line is divided by the long-run average level, so 1 means average. The model does not predict a level in ng/dL or nmol/L. It leaves out your own testosterone, your body size, the injection site and many other things that change real levels.

When are blood tests taken?

The dot on the chart marks the trough, the low point just before the next injection. It is one time a blood test can be taken, not the only one.

Guidance differs. The Endocrine Society (2018) says to measure midway between injections of cypionate or enanthate. The American Urological Association (2018) notes that levels have often been checked in the middle of the cycle and that the trough may also be useful. The Nebido label says to measure at the end of an injection interval.

Your prescriber decides when you test.

Terms used on this page

Ester: A chemical part attached to testosterone that slows how fast it leaves the injection spot. Cypionate and enanthate are examples.
Half-life: The time it takes for a level to drop by half. Here it means how fast the depot releases testosterone.
Peak: The highest level between two injections.
Trough: The lowest level between two injections, usually just before the next one.
Steady state: The point where each rise and fall looks the same as the last one.
Peak-to-trough ratio: The peak divided by the trough. A ratio of 2 to 1 means the highest level is twice the lowest.

Sources for each value

Every number in the model comes from the file of verified sources behind this page. Values marked as fitted or chosen are our assumptions, explained under each ester.

Quotes are shown as written in the source, in the source's own units.

Testosterone cypionate (injection into a muscle)

Half-life from the US label. Time to peak is the median from a single 200 mg injection study on the Azmiro label. The rise rate is calculated from these two values. The model uses the same values for enanthate, for the reason given under enanthate.

Half-life used: 8 daysStated in the source
DEPO-Testosterone (testosterone cypionate) injection, USP CIII, prescribing information, Clinical Pharmacology (DailyMed (U.S. National Library of Medicine), label effective 2026-08-21 (version 26))
“The half-life of testosterone cypionate when injected intramuscularly is approximately eight days.”
Time to peak used: 2.99 daysStated in the source
AZMIRO (testosterone cypionate) injection, prescribing information, section 12.3, Table 1 (DailyMed (U.S. National Library of Medicine), label effective 2025-07-25)
“Pharmacokinetic parameters of baseline-corrected testosterone obtained following a single-dose intramuscular administration of AZMIRO 200 mg in prefilled syringe in 26 hypogonadal adult males ... T max(hr) 71.7 (24.0, 191.0) a ... aReported in median (min, max).”

Testosterone enanthate (injection into a muscle)

The only head-to-head comparison of the two esters (Schulte-Beerbühl and Nieschlag, 1980) gave 6 healthy men one injection of enanthate and one of cypionate, each carrying the same amount of testosterone. It found nearly identical blood levels, as reported in Health Canada product monographs. So the model uses the cypionate half-life and time to peak for enanthate too, and both esters are drawn with the same curve. The head-to-head reported the peak earlier, on days 1 to 2 after the injection. The tool keeps the time to peak from a cypionate label: a median of about 3 days, ranging from 1 to 8 days, in the Azmiro study. The head-to-head was small, used a single injection and did not include men with low testosterone. Other published values for enanthate are listed below as not used in the model: a 7.19-day half-life and a time to peak measured once levels had settled (Kaminetsky 2015), and 4 to 5 days from the 2026 European Association of Urology guideline table.

Only head-to-head comparisonStated in the source
Testosterone Enanthate Injection, USP 200 mg/mL (Hikma Canada Limited) Prescribing Information, date of preparation March 17, 2023, Detailed Pharmacology, Absorption (page 11 of 17; the study is its reference 6, Schulte-Beerbuhl M et al., Fertility and Sterility 1980) (Health Canada Drug Product Database (DIN 02536315))
“Testosterone enanthate (194 mg) and testosterone cypionate (200 mg) were injected so that the amount of unesterified testosterone was the same in both preparations (140 mg). The serum testosterone levels were identical after both preparations.”
Only head-to-head comparisonStated in the source
Taro-Testosterone Cypionate Injection 100 mg/mL Product Monograph, date of revision May 26, 2022, Detailed Pharmacology (pages 12 to 13 of 20; the study is its reference 1, Schulte-Beerbuhl M, Nieschlag E, Fertil Steril 1980) (Health Canada Drug Product Database (Taro Pharmaceutical Inc.))
“In a randomized cross-over study of six healthy males aged 20-29 years of age, the pharmacokinetics of a single injection of 200 mg testosterone cypionate was compared to that of a single injection of 194 mg testosterone enanthate. Mean serum testosterone concentrations increased sharply to 3 times the basal levels (approximately 1350 ng/dL) at 24 hours and declined gradually to basal levels (approximately 500 ng/dL) by day 10.”
Half-life used: 8 daysSame value as cypionate
DEPO-Testosterone (testosterone cypionate) injection, USP CIII, prescribing information, Clinical Pharmacology (DailyMed (U.S. National Library of Medicine), label effective 2026-08-21 (version 26))
“The half-life of testosterone cypionate when injected intramuscularly is approximately eight days.”
Time to peak used: 2.99 daysSame value as cypionate
AZMIRO (testosterone cypionate) injection, prescribing information, section 12.3, Table 1 (DailyMed (U.S. National Library of Medicine), label effective 2025-07-25)
“Pharmacokinetic parameters of baseline-corrected testosterone obtained following a single-dose intramuscular administration of AZMIRO 200 mg in prefilled syringe in 26 hypogonadal adult males ... T max(hr) 71.7 (24.0, 191.0) a ... aReported in median (min, max).”
Other published half-life: 7.19 daysNot used in the model
Kaminetsky J, Jaffe JS, Swerdloff RS. Pharmacokinetic Profile of Subcutaneous Testosterone Enanthate Delivered via a Novel, Prefilled Single-Use Autoinjector: A Phase II Study. Sex Med 2015;3:263-273 (PMID 26797061) (Sexual Medicine (Wiley / ISSM); full text in PMC)
“The apparent T1/2 (SD) was 239.63 hours (59.93) for 100 mg SC TE and 172.57 hours (34.74) for 200 mg IM TE.”
Other published time to peak: 1.39 days (33 hours)Not used in the model
Kaminetsky 2015, Table 2 (steady-state PK parameters at week 6) (Sexual Medicine; full text in PMC)
“Mean Tmax—h (SD), 45.43 (33.60), 35.54 (30.40), 33.30 (24.52)”
Other published half-life: 4 to 5 daysNot used in the model
EAU Guidelines on Sexual and Reproductive Health, Chapter 3: Male Hypogonadism (2026 edition), Table 3.5: Available preparations for hypogonadism treatment (European Association of Urology (uroweb.org))
Guideline summary table, not a pharmacokinetic study
“Testosterone enanthate, 17-α-hydroxylester, 4-5 days, 250mg every 2-3 weeks”

Testosterone propionate (injection into a muscle)

The 20-hour half-life is from a summary table in the 2026 European Association of Urology guideline. The table does not name the study behind it, so treat it as a rounded guide value. No open source states a time to peak: a 12-hour peak sits inside the time range an older study reports. The rise rate is calculated from these two values.

Half-life used: 0.83 days (20 hours)Stated in the source
EAU Guidelines on Sexual and Reproductive Health, Chapter 3: Male Hypogonadism (2026 edition), Table 3.5: Available preparations for hypogonadism treatment (European Association of Urology (uroweb.org))
Guideline summary table, not a pharmacokinetic study
“Testosterone propionate, 17-α-hydroxylester, 20 hrs, 100mg every 2 days”
Time to peak used: 0.5 days (12 hours)Assumption based on published data
Fujioka M, Shinohara Y, Baba S, Irie M, Inoue K. Pharmacokinetic properties of testosterone propionate in normal men. J Clin Endocrinol Metab 1986;63(6):1361-4 (PMID 3782423) (PubMed abstract (Endocrine Society / OUP))
“The plasma levels of testosterone propionate-19,19,19-d3 were maintained at 2-4 ng/ml between 3 and 36 h after administration. Plasma testosterone-19,19,19-d3 levels were maintained above the physiological testosterone level for 48 h, while plasma levels of endogenous testosterone changed little.”

Testosterone undecanoate (long-acting injection into a muscle)

The Nebido label gives a release half-life of 90 days, give or take 40. With 90 days, the model's highs and lows would be flatter than the label's own steady-state numbers, so the model uses 50 days, which is inside that range. Time to peak is from the Aveed label.

Half-life used: 50 daysFitted to published data (assumption)
Nebido 1000 mg/4 ml solution for injection, SmPC section 5.2 (electronic medicines compendium (emc), text revised 15/12/2025)
“Following intramuscular administration of this depot formulation the release rate is characterised by a half life of 90±40 days.”
Time to peak used: 7 daysStated in the source
AVEED prescribing information, section 12.3 (DailyMed (U.S. National Library of Medicine), label effective 2025-07-15)
“Following intramuscular injection of 750 mg of AVEED, serum testosterone concentrations reach a maximum after a median of 7 days (range 4 to 42 days) then slowly decline (Figure 3).”
Data used for the fitFitted to published data (assumption)
Nebido SmPC section 5.2 (steady-state Cmax and Cmin) (emc)
“After the 1 st intramuscular injection of 1000 mg testosterone undecanoate to hypogonadal men, mean Cmax values of 38 nmol/L (11 ng/mL) were obtained after 7 days. ... Mean Cmax and Cmin values of testosterone at steady-state were about 37 (11 ng/mL) and 16 nmol/L (5 ng/mL), respectively.”
Label scheduleStated in the source
AVEED prescribing information, section 2.1 (DailyMed)
“The recommended dose of AVEED is 3 mL (750 mg) injected intramuscularly, followed by 3 mL (750 mg) injected after 4 weeks, then 3 mL (750 mg) injected every 10 weeks thereafter.”
Label scheduleStated in the source
Nebido SmPC section 4.2 (emc)
“One ampoule / vial of Nebido (corresponding to 1000 mg testosterone undecanoate) is injected every 10 to 14 weeks. Injections with this frequency are capable of maintaining sufficient testosterone levels and do not lead to accumulation. ... the first injection interval may be reduced to a minimum of 6 weeks as compared to the recommended range of 10 to 14 weeks for maintenance.”

Sustanon 250 (blend of four esters)

No open source gives a half-life for each of the four esters. The blend is drawn as one curve: the peak at 1.5 days is the middle of the label's 24 to 48 hours, and the 6.9-day half-life brings levels back to the low end of normal in about 21 days, as the label describes.

What is in the blendStated in the source
Sustanon 250, 250mg/ml solution for injection, SmPC section 2 (electronic medicines compendium (emc), date of revision Dec 2025)
“Each ampoule contains 1 ml arachis oil (refined), containing the following active substances: - 30 mg Testosterone propionate - 60 mg Testosterone phenylpropionate - 60 mg Testosterone isocaproate - 100 mg Testosterone decanoate All four components are esters of the natural hormone testosterone. The total amount of testosterone per ml is 176 mg.”
Half-life used: 6.9 daysFitted to published data (assumption)
Sustanon 250 SmPC section 5.2 (Absorption) (emc)
“A single dose of Sustanon 250 leads to an increase of total plasma testosterone with peak levels of approximately 70nmol/l (Cmax), which are reached approximately 24-48 h (tmax) after administration. Plasma testosterone levels return to the lower limit of the normal range in males in approximately 21 days.”
Time to peak used: 1.5 days (36 hours)Assumption based on published data
Sustanon 250 SmPC section 5.2 (Absorption) (emc)
“A single dose of Sustanon 250 leads to an increase of total plasma testosterone with peak levels of approximately 70nmol/l (Cmax), which are reached approximately 24-48 h (tmax) after administration. Plasma testosterone levels return to the lower limit of the normal range in males in approximately 21 days.”
Label scheduleStated in the source
Sustanon 250 SmPC section 4.2 (electronic medicines compendium (emc), date of revision Dec 2025)
“Usually, one injection of 1ml per 3 weeks is adequate.”

Testosterone in the blood

This is how fast testosterone itself leaves the blood. The model does not use it, because after an injection the slow release from the depot sets the pace.

Cleared in about 10 to 100 minutesStated in the source

Testosterone Enanthate Injection, USP (Hikma) prescribing information, Clinical Pharmacology (DailyMed (U.S. National Library of Medicine), label effective 2026-05-08)

“There are considerable variations of the half-life of testosterone as reported in the literature, ranging from 10 to 100 minutes.”

What we could not verify

Separate half-lives for the four esters in Sustanon 250.
A half-life for testosterone propionate measured in a study. The model uses a guideline table value.
The study behind the widely repeated 4.5-day half-life for enanthate. A guideline table lists 4 to 5 days.
The full text of the 1980 study that compared cypionate and enanthate. Its results are known here only from the Health Canada monographs that report it.