Testosterone esters explained: cypionate, enanthate and more

Testosterone esters are testosterone molecules carrying an attached fatty acid chain, and that chain sets how fast the hormone is released after injection. Anderson 1993 in Human Reproduction found a single propionate injection peaked at 8 hours and was back to baseline within 4 days. Longer chains stretch that release across weeks.

Key takeaways

• Bi 2018 in CPT: Pharmacometrics and Systems Pharmacology, a randomized double-blind study in 31 healthy men, described cypionate with a linear one-compartment model, population mean clearance 2.6 kL/day and volume of distribution 14.4 kL.
• Dobs 1999 in the Journal of Clinical Endocrinology and Metabolism, a 24-week randomized trial in 66 hypogonadal men, found enanthate every 2 weeks gave supraphysiological levels for several days after each injection, with mean morning levels in the normal range in 19 to 84 percent of injection patients versus 77 to 100 percent of patch patients.
• No head-to-head trial of cypionate against enanthate by the same route exists, so any claim that one is better is unsupported.
• Wang 2010 in the Journal of Andrology, an 84-week single-arm study in 130 men, found long-acting injectable undecanoate held average trough concentrations at 300 to 1000 ng/dL, but that product has never been authorized in Canada.
• Nackeeran 2022 in The Journal of Urology, pooling 29 randomized trials and 3,393 men, found mean hematocrit increases versus placebo of 4.0 percent for intramuscular enanthate or cypionate, 3.0 percent for gel, 1.6 percent for intramuscular undecanoate and 1.4 percent for the patch.
• Only two injectable testosterone products were marketed in Canada at the Health Canada Drug Product Database check of 14 September 2026: a cypionate 100 mg/mL solution and an enanthate 200 mg/mL solution.

Who does this evidence apply to?

All of it applies to men with confirmed low testosterone. Health Canada’s product monograph for oral testosterone undecanoate, authorized 12 December 2025, requires deficiency to be clearly demonstrated by clinical features and confirmed by two separate validated biochemical assays of morning testosterone. What testing your own case needs is a decision for your doctor or nurse practitioner.

None of it applies to men whose testosterone is normal. The same monograph states the product should not be used for non-specific symptoms suggestive of hypogonadism if deficiency has not been demonstrated. For the diagnostic steps, see how low testosterone is diagnosed in Canada.

What do testosterone esters actually do?

They slow the release of the hormone from the injection site. Testosterone on its own is poorly used when swallowed or injected, so the molecule is joined to a fatty acid chain that must be cleaved before the hormone becomes active. The longer and more fat-soluble the chain, the slower the depot empties.

That single property is what separates a weekly injection from a ten-week one. It is not a difference in the hormone itself: once the ester is cleaved, the testosterone reaching the blood is the same molecule.

What is known about testosterone cypionate?

The best human data come from healthy volunteers rather than patients. Bi 2018 in CPT: Pharmacometrics and Systems Pharmacology reported a randomized double-blind trial with population modelling in 31 healthy men who received 14 weekly injections at 100, 250 or 500 mg per week. A linear one-compartment model best described the concentration-time profile, with a population mean clearance of 2.6 kL/day and a volume of distribution of 14.4 kL. Body weight and albumin were significant covariates, and the estimated potency for suppression of luteinizing hormone synthesis was 9.33 ng/mL.

Suppression of endogenous testosterone, luteinizing hormone and sperm production was, in the authors’ words, more severe and of greater duration in the 250 mg and 500 mg groups.

The limitation matters. Bi 2018 studied healthy volunteers, and there is no other human cypionate pharmacokinetic study with clean peak and trough numbers in hypogonadal men. Precise cypionate peak and trough figures for patients go beyond the published record.

In Canada, cypionate is now a single marketed generic, Taro-Testosterone Cypionate Injection 100 mg/mL, DIN 02496003, verified in the Health Canada Drug Product Database on 14 September 2026. A second cypionate 100 mg/mL product from SteriMax, DIN 02570122, was approved on 20 July 2026 but is not marketed. The brand product Depo-Testosterone, DIN 00030783, was cancelled post market on 18 July 2025.

What is known about testosterone enanthate?

Enanthate has the clearest evidence on what a two-weekly injection pattern looks like. Dobs 1999 in the Journal of Clinical Endocrinology and Metabolism ran a 24-week randomized parallel-group trial in 66 hypogonadal men, comparing a permeation-enhanced patch against 200 mg of enanthate given intramuscularly every 2 weeks.

The injection arm, in the authors’ words, produced supraphysiological levels of testosterone, bioavailable testosterone and estradiol, though not dihydrotestosterone, for several days after each injection. Mean morning sex hormone levels were within the normal range in 77 to 100 percent of patch patients versus 19 to 84 percent of intramuscular patients. Luteinizing hormone was suppressed into the subnormal range in 31 percent of intramuscular patients versus 0 percent of patch patients.

That is the measured basis for describing two-weekly injections as a peak and trough pattern. Note what the comparison was: a patch product no longer available in Canada, the United States, the United Kingdom or Australia. The trial describes the injection curve well, but it does not compare enanthate against any option a Canadian reader can obtain today.

In Canada, enanthate is marketed as Testosterone Enanthate Injection USP 200 mg/mL from Hikma Canada, DIN 02536315, verified on 14 September 2026. The former brand product Delatestryl, DIN 00029246, was cancelled post market on 18 December 2025. Canadian content still listing either cancelled brand is out of date. The current marketed list is in which testosterone products are available in Canada.

Is cypionate or enanthate better?

Unknown. PubMed returns no head-to-head pharmacokinetic or clinical trial of cypionate against enanthate by the same route, checked 14 September 2026.

The nearest comparison, Choi 2021 in The Journal of Urology, set intramuscular cypionate against subcutaneous enanthate in 234 hypogonadal men. Because ester and route both change between the arms, it cannot separate one from the other. See what the evidence says about testosterone injections.

No trial has measured whether the chemical difference between the two esters translates into any difference a patient would notice. Stating that plainly is more accurate than inventing one.

What is known about long-acting testosterone undecanoate injection?

This is the ester designed for very long intervals, and it has never been authorized in Canada. Every testosterone undecanoate product with a Canadian DIN is an oral capsule. The long-acting castor oil injection is available in the United Kingdom, Australia and the United States, where it carries a restricted-distribution safety program.

Wang 2010 in the Journal of Andrology followed 130 men with total testosterone below 300 ng/dL through 9 injections of 750 mg over 84 weeks, given at weeks 0 and 4 and then every 10 weeks. Patients maintained average trough concentrations in the adult male range of 300 to 1000 ng/dL, or 10.4 to 34.7 nmol/L, before each injection, and free testosterone, dihydrotestosterone and estradiol remained relatively consistent once steady state was reached. The trial was unblinded and single arm.

Nieschlag 1999 in Clinical Endocrinology gave 13 hypogonadal men four 1000 mg injections at 6-week intervals over 24 weeks. Testosterone was never found below the lower limit of normal, and only briefly after the third and fourth injections above the upper limit of normal. Estradiol and dihydrotestosterone did not exceed normal limits. The study was small and open label.

von Eckardstein 2002 in the Journal of Andrology followed 7 men for 3.2 years on 1000 mg at 12-week intervals. Testosterone peaked one week after injection at 32.0 plus or minus 11.7 nmol/L and measured 12.6 plus or minus 3.7 nmol/L before the last injection. Body weight, hemoglobin, lipids, prostate specific antigen and prostate volume did not change significantly. With 7 participants, this is a signal, not proof.

Minnemann 2008 in the Journal of Endocrinological Investigation is the closest thing to a head-to-head ester trial that exists: an open-label randomized study in 40 men comparing enanthate 250 mg every 3 weeks against undecanoate 1000 mg every 6 to 9 weeks for 30 weeks, after which 32 men continued on undecanoate every 12 weeks to 114 weeks. Hemoglobin and hematocrit rose significantly in both groups over the first 30 weeks, then plateaued, and did not exceed the upper limit of normal. The authors concluded that undecanoate every 12 weeks was at least as safe and efficacious as enanthate, at a substantially lower frequency of administration.

Why is testosterone propionate not used for replacement?

Because it clears too quickly. Anderson 1993 in Human Reproduction gave 12 healthy men a single 100 mg intramuscular injection and reported that the injection caused a rapid 3 to 4-fold increase in plasma testosterone concentrations, which was at a maximum at 8 hours and had returned to baseline within 4 days.

A compound that is gone within 4 days cannot hold a steady level between practical injection intervals. That measurement, taken incidentally in a study asking a different question, is the whole argument against propionate as a replacement ester.

No modern human pharmacokinetic study of propionate in hypogonadal men exists. In Canada the SteriMax propionate product, DIN 01977571, has been dormant since 2017.

What are mixed-ester injections and can Canadians get them?

A mixed-ester injection combines several esters in one ampoule so that short and long chains release at different rates. The Sustanon-type product contains propionate, phenylpropionate, isocaproate and decanoate at a combined 250 mg/mL. It is available in neither Canada nor the United States. It is authorized in the United Kingdom under PL 39699/0059, in place since 1973, and in Australia under ARTG 14521 and 190717, both verified on 14 September 2026.

No modern comparative trial of a mixed-ester product against a single ester was retrieved, so this is a product fact about other countries rather than an evidence claim. The full country-by-country picture is in testosterone products by country.

Does the choice of ester change the effect on hematocrit?

This is the one comparative safety outcome with usable numbers. Nackeeran 2022 in The Journal of Urology pooled 29 placebo-controlled randomized trials covering 3,393 men in a Bayesian network meta-analysis of hematocrit change by formulation.

Read the comparison carefully. When formulations were compared against each other rather than against placebo, intramuscular cypionate or enanthate was associated with a significantly higher increase than the patch, and no other between-formulation difference was detected. The authors stated that the clinical concern of this increase remains questionable, and that theirs was the first network meta-analysis to attempt it given the absence of head-to-head trials. See hematocrit and testosterone by formulation.

What the evidence does not show

• It does not show that cypionate and enanthate differ. No head-to-head trial of the two esters by the same route was found on PubMed as of 14 September 2026.
• It does not show what injection interval is best for any short-acting ester. No randomized trial compares injection frequencies of the same short-acting ester, so there is no trial of weekly against every-two-week cypionate, and none of split or daily schedules.
• It does not establish long-acting undecanoate on strong evidence. Wang 2010 was unblinded and single arm across 130 men, Nieschlag 1999 enrolled 13, von Eckardstein 2002 enrolled 7, and Minnemann 2008 was open label with 40.
• It does not give cypionate peak and trough figures for patients. Bi 2018 studied 31 healthy volunteers, and no equivalent study in hypogonadal men was found.
• It does not show that most esters differ on hematocrit. In Nackeeran 2022, only the comparison between intramuscular short esters and the patch reached significance among 3,393 men in 29 trials.
• It does not settle the comparative question generally. Madsen 2022 in Endocrine Connections reported that hardly any comparative studies have been carried out, and that current recommendations appear to rest primarily on non-randomized and observational data.

Frequently asked questions

What is a testosterone ester?

A testosterone ester is a testosterone molecule with a fatty acid chain attached to it, which must be cleaved off before the hormone becomes active. The chain controls how fast the hormone is released from an injection site. Anderson 1993 in Human Reproduction measured a propionate injection returning to baseline within 4 days, while Wang 2010 in the Journal of Andrology measured undecanoate holding trough levels across 10-week intervals.

Is cypionate better than enanthate?

There is no evidence either way. PubMed returns no head-to-head pharmacokinetic or clinical trial of cypionate against enanthate by the same route, checked on 14 September 2026. The one comparative study, Choi 2021 in The Journal of Urology with 234 men, changed both the ester and the route between arms, so it cannot answer the question. Any confident claim that one ester outperforms the other is not based on a trial.

Can I get the long-acting undecanoate injection in Canada?

No. The long-acting testosterone undecanoate injection has never been authorized in Canada, and every testosterone undecanoate product with a Canadian DIN is an oral capsule, verified in the Health Canada Drug Product Database on 14 September 2026. The injection is authorized in the United Kingdom, Australia and the United States. No public reason is on record for why it was never authorized here.

Why is propionate not used any more?

Its release is too short to maintain a steady level. Anderson 1993 in Human Reproduction gave 12 healthy men a single 100 mg intramuscular injection and found a rapid 3 to 4-fold rise in plasma testosterone that peaked at 8 hours and returned to baseline within 4 days. In Canada the SteriMax propionate product, DIN 01977571, has been dormant since 2017, and no modern pharmacokinetic study of propionate in hypogonadal men exists.

Which injectable esters are actually sold in Canada?

Two, as verified in the Health Canada Drug Product Database on 14 September 2026: a cypionate 100 mg/mL solution from Taro, DIN 02496003, and an enanthate 200 mg/mL solution from Hikma Canada, DIN 02536315. Both former brand injectables were cancelled post market in 2025, Depo-Testosterone, DIN 00030783, on 18 July 2025 and Delatestryl, DIN 00029246, on 18 December 2025. A second cypionate product was approved on 20 July 2026 but is not yet marketed.

References

1. Bi Y, et al. 2018. Population Pharmacokinetic/Pharmacodynamic Modeling of Depot Testosterone Cypionate in Healthy Male Subjects. CPT: Pharmacometrics and Systems Pharmacology. PMID 29436172. DOI: https://doi.org/10.1002/psp4.12287
2. Dobs AS, et al. 1999. Pharmacokinetics, efficacy, and safety of a permeation-enhanced testosterone transdermal system in comparison with bi-weekly injections of testosterone enanthate for the treatment of hypogonadal men. Journal of Clinical Endocrinology and Metabolism. PMID 10522982. DOI: https://doi.org/10.1210/jcem.84.10.6078
3. Wang C, et al. 2010. Pharmacokinetics and safety of long-acting testosterone undecanoate injections in hypogonadal men: an 84-week phase III clinical trial. Journal of Andrology. PMID 20133964. DOI: https://doi.org/10.2164/jandrol.109.009597
4. Nieschlag E, et al. 1999. Repeated intramuscular injections of testosterone undecanoate for substitution therapy in hypogonadal men. Clinical Endocrinology. PMID 10619981. DOI: https://doi.org/10.1046/j.1365-2265.1999.00881.x
5. von Eckardstein S, et al. 2002. Treatment of male hypogonadism with testosterone undecanoate injected at extended intervals of 12 weeks: a phase II study. Journal of Andrology. PMID 12002444. No DOI in the PubMed record.
6. Minnemann T, et al. 2008. Comparison of a new long-acting testosterone undecanoate formulation vs testosterone enanthate for intramuscular androgen therapy in male hypogonadism. Journal of Endocrinological Investigation. PMID 18852533. DOI: https://doi.org/10.1007/BF03346421
7. Anderson RA, et al. 1993. Human Reproduction. PMID 8288743. DOI: https://doi.org/10.1093/oxfordjournals.humrep.a137940
8. Choi EJ, et al. 2021. Comparison of Outcomes for Hypogonadal Men Treated with Intramuscular Testosterone Cypionate versus Subcutaneous Testosterone Enanthate. The Journal of Urology. PMID 34694927. DOI: https://doi.org/10.1097/JU.0000000000002301
9. Nackeeran S, et al. 2022. The Effect of Route of Testosterone on Changes in Hematocrit: A Systematic Review and Bayesian Network Meta-Analysis of Randomized Trials. The Journal of Urology. PMID 34445892. DOI: https://doi.org/10.1097/JU.0000000000002188
10. Madsen MC, et al. 2022. Testosterone in men with hypogonadism and transgender males: a systematic review comparing three different preparations. Endocrine Connections. PMID 35904217. DOI: https://doi.org/10.1530/EC-22-0112
11. Health Canada. Drug Product Database. Queried 14 September 2026. https://health-products.canada.ca/dpd-bdpp/search/
12. Health Canada. Product Monograph, oral testosterone undecanoate capsules. Authorized 12 December 2025. https://pdf.hres.ca/dpd_pm/00082762.PDF
13. Therapeutic Goods Administration. Australian Register of Therapeutic Goods. Queried 14 September 2026. https://www.tga.gov.au/resources/artg

This page is educational information, not medical advice. Testosterone is a prescription medication and a controlled substance in Canada. Talk to your doctor or pharmacist about your own situation.