Injectable AAS / IM, SubQ / 100-500mg per week
Testosterone Cypionate
Testosterone was isolated and synthesized in 1935, and the first injectable ester, propionate, wore off in days. Cypionate was Upjohn's answer to that problem: a heavier tail that stretched one injection from days to weeks, sold in the United States as Depo-Testosterone and still the most familiar injectable testosterone there.
In plain words
Testosterone cypionate is ordinary testosterone with a fatty tail attached, which makes it dissolve in oil; injected into muscle or under the skin it forms a small depot that releases the hormone over days instead of hours, and enzymes then clip the tail off so that what acts on the body is plain testosterone. It has been an approved prescription drug in the United States since the early 1950s, sold as Depo-Testosterone, and it is still the most familiar injectable testosterone there. Its current label covers only two specific disease causes of low testosterone, states that safety and efficacy in age-related low testosterone have not been established, and testosterone and its esters were made Schedule III controlled substances there by a law signed in 1990. The kinetics have been measured directly: in the published study a single 200 mg injection into muscle raised blood testosterone about threefold, with many of the men above the normal range from day 2 through day 7 before levels fell back to where it started by day 13 or 14. The muscle-building effects of testosterone are established by randomized trials, but the wider safety picture is less settled: pooling 51 comparative trials, the dependable finding was a rise in red cell mass, with no detectable effect on deaths, prostate or heart outcomes - though the authors rated that evidence low to medium quality with follow-up of only 3 months to 3 years, so no detected effect is not the same as proof of safety.
At a glance
| Half-life | 6.9 days |
|---|---|
| Tmax | 4.5 days |
| Route(s) | IM, SubQ |
| Published dosing range | 100-500mg per week |
Reference data from the DosePlot canon -- not a protocol recommendation.
Serum curve
Single 300 mg dose by IM, rendered from the same engine that powers the interactive chart. Relative levels, not lab values.
What does the evidence show?
Two things are labeled separately here because they answer different questions. The tier is how a study was built. The distance chips are whether that study touched this molecule, by this route, in a population resembling the reader. A randomized trial of a different molecule keeps its tier and still says nothing about this compound.
| Finding | Tier | Distance from use | Study |
|---|---|---|---|
| A single 200 mg intramuscular injection raises serum testosterone about threefold in hypogonadal men. The study reports peak serum testosterone on days 2 to 5, and reserves days 4 to 5 for the peak of absolute non-SHBG-bound testosterone. Many of the 11 men sat above the normal range from day 2 to day 7, and values declined to basal levels by days 13 to 14. The cohort mixed men receiving their first injection with men already on chronic cypionate, so that day 13 to 14 floor is the group's own basal level, not an untreated hypogonadal baseline. | clinical | not recorded | Nankin HR. Hormone kinetics after intramuscular testosterone cypionate.Fertility and Sterility 47(6):1004-1009, 1987 |
| The same injection raises estradiol about threefold over days 2 to 7, because part of the released testosterone is aromatized. Luteinizing hormone is suppressed after the first injection and stays suppressed on continued treatment. | clinical | not recorded | Nankin HR. Hormone kinetics after intramuscular testosterone cypionate.Fertility and Sterility 47(6):1004-1009, 1987 |
| Subcutaneous injection reaches the normal male range. In a retrospective cohort of 63 transgender men given weekly subcutaneous testosterone cypionate or enanthate at 50 to 150 mg (median 75 to 80 mg), all 63 reached serum testosterone inside the normal male range, across body mass indexes from 19.0 to 49.9. Minor transient site reactions were reported in 9 of 63. Of the 22 who had been injecting intramuscularly and switched, all 22 preferred the subcutaneous route, 20 of them markedly. The study ran no concurrent intramuscular arm, so it establishes that the subcutaneous route works and that patients prefer it, not that the two routes are equally reliable. | clinical | not recorded | Spratt DI, Stewart II, Savage C, et al. Subcutaneous injection of testosterone is an effective and preferred alternative to intramuscular injection: demonstration in female-to-male transgender patients.Journal of Clinical Endocrinology and Metabolism 102(7):2349-2355, 2017 |
| On a weekly subcutaneous schedule, mean levels stay flat between injections. Eleven transgender men already stable on weekly subcutaneous testosterone cypionate were sampled at eight points across one dosing week. The seven samples taken between injections averaged 627 ng/dL total testosterone (standard deviation 206), and mean total and free testosterone stayed well inside the normal range across the interval. Individual values spanned 205 to 1410 ng/dL, so the flatness is a property of the group mean rather than of every patient at every hour. | clinical | not recorded | McFarland J, Craig W, Clarke NJ, Spratt DI. Serum testosterone concentrations remain stable between injections in patients receiving subcutaneous testosterone.Journal of the Endocrine Society 1(8):1095-1103, 2017 |
| Weekly injection of a testosterone ester at supraphysiologic dose adds muscle even without training. In a randomized placebo-controlled trial, 600 mg per week of testosterone enanthate (the sister ester, with closely matched release kinetics) for 10 weeks increased triceps and quadriceps cross-sectional area and bench-press and squat strength in men who did not exercise; combined with lifting it added 6.1 kg of fat-free mass. | rct | not recorded | Bhasin S, Storer TW, Berman N, et al. The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men.New England Journal of Medicine 335(1):1-7, 1996 |
| The reliable adverse effect of testosterone treatment is a rise in red cell mass. Pooling 51 comparative trials, treatment raised hemoglobin by 0.80 g/dL and hematocrit by 3.18 percentage points and lowered HDL cholesterol by about 0.5 mg/dL, with no detectable effect on mortality, prostate, or cardiovascular outcomes. The authors rated the underlying evidence low to medium quality with follow-up of 3 months to 3 years, so the absence of an effect is not the same as proof of safety. | clinical | not recorded | Fernandez-Balsells MM, Murad MH, Lane M, et al. Clinical review 1: adverse effects of testosterone therapy in adult men: a systematic review and meta-analysis.Journal of Clinical Endocrinology and Metabolism 95(6):2560-2575, 2010 |
| Splitting the labeled 2 to 4 week interval into weekly or twice-weekly injections, frequently subcutaneous with an insulin syringe, is the standard community practice. It is reported to blunt both the first-week peak symptoms and the flat stretch before the next dose. | anecdotal | not recorded | community reports aggregated from reddit, MESO-Rx, and similar forumsno study |
How did it get here?
- preclinical1935
- Testosterone is isolated from testicular extract by Laqueur's laboratory in Amsterdam and, in the same year, synthesized by two competing groups (Butenandt and Hanisch; Ruzicka and Wettstein), work that takes the 1939 Nobel Prize in Chemistry. Both syntheses start from cholesterol, by way of dehydroandrosterone. The plant-sterol semi-synthesis that later supplies the steroid industry is a separate development, decades younger. Every later product is a modification of this one molecule.
- first-human1937-1949
- Testosterone propionate becomes the first widely used injectable form. It works, but its short ester means injections every two or three days, which is what sends manufacturers looking for a heavier tail.
- clinical-adoptionearly 1950s
- Upjohn introduces testosterone cypionate in the United States as Depo-Testosterone. The cyclopentylpropionate ester turns a two-day drug into a two-week one, and cypionate becomes the default injectable testosterone in American practice, a regional habit that has never fully spread to Europe, where enanthate dominates.
- clinical-adoption1980
- Schulte-Beerbuhl and Nieschlag publish a head-to-head comparison of serum testosterone, dihydrotestosterone, LH and FSH after injection of enanthate versus cypionate (Fertility and Sterility 33(2):201-203). From this period on the two esters are treated as clinically interchangeable, and DosePlot's reference record reflects that: near-identical half-life and time to peak.
- grey-market1990
- The Anabolic Steroids Control Act is signed in November 1990 and takes effect in February 1991, moving testosterone and its esters into Schedule III. Prescription supply continues unchanged. Non-prescription supply moves to underground labs, where the chemistry is old enough to copy but the sterile filling and batch testing are not, so identity, potency, and sterility stop being guaranteed.
- clinical-adoption2014-2020s
- Regulation tightens, then data catch up with practice. After a decade of anti-aging and compounding-clinic prescribing, the Depo-Testosterone insert is revised five times between March and August 2015; the current insert indicates only primary and hypogonadotropic hypogonadism, states that safety and efficacy in age-related, or late-onset, hypogonadism have not been established, requires two morning serum testosterone measurements before starting, and carries a drug abuse and dependence section plus a paragraph calling the evidence on major adverse cardiovascular events inconclusive. Two 2017 reports from one group in Maine then show the subcutaneous route works: 63 patients on weekly subcutaneous cypionate or enanthate all reached the normal male range, and 11 patients on weekly subcutaneous cypionate held mean levels flat across the dosing week. Telehealth clinics normalize weekly or twice-weekly dosing. The package insert still reads 50 to 400 mg every two to four weeks.
How is it made?
Production happens in three stages.
1. Making the testosterone. Almost no commercial testosterone is extracted from animals. It is semi-synthesized from plant sterols, usually the phytosterols in soy or the diosgenin in wild yam. Industrial chemistry strips the plant molecule down to a common steroid backbone, then converts it to testosterone through a short, well-established reaction sequence, the same route behind most of the world's steroid medicines since the 1960s.
2. Attaching the cypionate ester. Testosterone is reacted with cyclopentylpropionic acid, which bonds an eight-carbon tail to the molecule at its 17-beta position. The tail is the entire point of the product: it makes the molecule dissolve in oil instead of water, so after injection it sits in the oil depot in the muscle and leaves slowly. Esterases in blood and tissue then clip the tail off, releasing active testosterone over days rather than hours. The tail is also dead weight, about 30 percent of the injected milligrams.
3. Filling the vial. The ester is dissolved in a carrier oil (cottonseed oil in the US reference product), with benzyl benzoate to keep it in solution and benzyl alcohol as a preservative. The solution is sterile-filtered and filled into vials. Pharmaceutical production runs under GMP rules: every batch is tested for identity, potency, sterility, and endotoxins. The chemistry itself is old and well understood. The hard part of making a safe product is the sterile filling and batch testing, which is exactly the part that varies most outside regulated manufacturing.
Worth knowing
The name is a contraction of cyclopentanepropionate. The label's chemical name for the molecule is androst-4-en-3-one, 17-(3-cyclopentyl-1-oxopropoxy)-, at the 17-beta position, and its molecular weight is 412.61 against 288.4 for testosterone itself. That ratio is the practical part: about 70 percent of the milligrams in the syringe are testosterone and the remaining 30 percent is the tail that gets cleaved off and thrown away. A 200 mg injection delivers roughly 140 mg of testosterone. Enanthate, with a lighter seven-carbon tail, delivers about 72 mg per 100 mg.
Depo-Testosterone (testosterone cypionate injection, solution) prescribing information, DESCRIPTION section.Pharmacia and Upjohn Company LLC, US FDA label, revised August 2026
The oil in the vial is not only oil. The 100 mg/mL strength carries 736 mg of cottonseed oil, 0.1 mL of benzyl benzoate and 9.45 mg of benzyl alcohol per mL; the 200 mg/mL strength carries 560 mg of cottonseed oil and twice the benzyl benzoate, 0.2 mL per mL, because the higher drug load needs more co-solvent to stay dissolved. The stronger vial is therefore a chemically different injection, not simply a concentrated one.
Depo-Testosterone (testosterone cypionate injection, solution) prescribing information, DESCRIPTION section.Pharmacia and Upjohn Company LLC, US FDA label, revised August 2026
The dosing interval on the label predates the kinetic data that describe it. The insert still says 50 to 400 mg every two to four weeks, while the 1987 study that measured the curve concluded that 200 mg every two weeks produces wide variations in circulating androgen, from above-normal in the first week down to the cohort's own basal levels by days 13 to 14. Weekly dosing was worked out in practice long before it appeared in any labeling.
Nankin HR. Hormone kinetics after intramuscular testosterone cypionate.Fertility and Sterility 47(6):1004-1009, 1987
Written and reviewed by Evan Marlow, developer of DosePlot · Updated 2026-08-27
Not medical advice. DosePlot is an informational tool, not a healthcare provider, and using it creates no provider-patient relationship. Do not start, stop, or change any protocol without the approval of a licensed healthcare professional.
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