The Peptide Desk The Peptide Desk

This information is for research and educational purposes only. No medical recommendations. Products are not approved for human use. For health questions, consult a doctor.

Lexicon
Muscle & performance

Testosterone Cypionate

The second big long testosterone ester - practically identical to test enanthate.

1 min read 8 sources

To the product To the sources
Glass vial with clear pale yellow oil and a black TPD label on a white podium, next to it a blue 3D steroid molecule with an ester chain in a bright lab
Approved · since 1978Lab tested in the shop

Summary

At a glance

Sources checked on 26 Oct 2026

Back to baseline
13 days

After one injection: peak on days 2 to 5, back to baseline after 13 to 14 days2

Free testosterone on days 2 to 3
4.5 x

Rise after one injection in 11 men with hypogonadism, total testosterone threefold2

Haematocrit above 50 percent
66.7 %

Men on injections (cypionate or enanthate), on gel 12.8 percent3

Preferred subcutaneous
22 of 22

Clinic review of 63 people, all reached normal male levels4

Phase 3 in the registry
1 trial

plus 19 in phase 2, most on prostate cancer, as of 26 Oct 20267

  • Testosterone Cypionate is testosterone with a cypionate ester. It is only one carbon atom longer than enanthate and acts on the androgen receptor.8
  • After one injection the testosterone level tripled on days 2 to 5. It was back at baseline after 13 to 14 days, so levels swung widely with an injection every two weeks.2
  • Estradiol rose threefold in the same period. In a three-year review two thirds of men on injections had a haematocrit above 50 percent, on gel only 12.8 percent.23
  • Injected under the skin, all 63 people in a clinic review reached normal male levels and all 22 with intramuscular experience preferred subcutaneous.4
  • On the registry most trials deliberately test very high levels in prostate cancer. According to ChEMBL cypionate has been an approved drug since 1978. Everything here is the state of research, not a recommendation.758
Profile

Updated June 2026

How long does it stay in the body?

Share left after one dose, calculated with a half-life of ~5.5 days

Half-life ~5.5 days
After 11 days: 25 %
Day 6 · 47 %Day 11 · 25 %Day 17 · 11.7 %Day 28 · 2.9 %

Simplified model without an absorption phase, half-life from the TPD lexicon. The lexicon gives 5 to 6 days, we calculate with the middle.

Class
Testosterone ester

long-acting

Use
Intramuscular or subcutaneous

1-2x per week

Half-life
about 5-6 days
WADA
banned

anabolic

Sizes
3 sizes

50mg/ml, 250mg/ml, 200mg/ml

Contents 14 sections
  1. At a glance
  2. What is Testosterone Cypionate?
  3. How it works
  4. Cypionate vs enanthate
  5. Dosing
  6. What the research shows
  7. Research status
  8. Side effects
  9. Storage
  10. PCT / after coming off
  11. Related compounds
  12. FAQ
  13. Glossary
  14. Sources

What is Testosterone Cypionate?

Testosterone Cypionate (Test C) is testosterone with a cypionate ester. In practice it is nearly identical to Testosterone Enanthate - the esters differ by just one carbon atom, the half-life is marginally longer. In the US, cypionate is the traditionally more common TRT ester, in Europe it tends to be enanthate.

This information is for research and educational purposes only. No medical advice.

How it works

Identical to test enanthate: androgen receptor activation, increased protein synthesis, nitrogen retention and erythropoiesis. Partial conversion to estradiol via aromatase.

Where it acts

One receptor, several organs

Tap a point or a card. Grey = effect seen in trials.

  1. Hypothalamus and pituitary

    LH suppressed from the first injection, stayed suppressed with ongoing use2

    Observed in trials
  2. Blood

    Haematocrit above 50 percent more often with injections than with gel or pellets3

    Observed in trials
  3. Liver and blood lipids

    Cholesterol, LDL and triglycerides changed only temporarily, HDL stayed the same3

    Observed in trials
  4. Skeletal muscle

    Muscle size and strength increased, study with enanthate (same testosterone once the ester is split off)1

    Observed in trials

Targets in the ChEMBL database8

Compound CHEMBL1201101: one recorded mechanism, agonist with direct binding to the human receptor.

Androgen receptor
Gene
AR
UniProt
P10275
ChEMBL
CHEMBL1871
Action
Agonist, direct binding
Blue 3D molecules float from a glass sphere onto bright, blue shimmering fibres, one of them inside a clear bubble
Once the ester is split off, testosterone acts on the androgen receptor. Symbolic image.

Cypionate vs enanthate

The practical difference is negligible. Cypionate has a marginally longer half-life, both are injected 1-2x per week. If one works for you, so does the other. The choice is usually a matter of availability and habit.

Comparison

Short and long esters

The same compound at the same receptor with esters of different length, as stated in the TPD lexicon. Tap a card to open its entry.

Short ester Testosterone Propionate AR Medium ester Testosterone Phenylpropionate AR Long ester Testosterone Enanthate AR
Long ester Testosterone Cypionate AR
Very long ester Testosterone Decanoate AR Ultra-long ester Testosterone Undecanoate AR

Dosing

Dosing

Dosing, titration and syringe

Loading the dosing information …

  • Getting started and stepping up, drawn as a staircase
  • Units on the U-100 syringe for every step
  • How long one vial lasts

What the research shows

Testosterone research applies to all esters equally, because once the ester is cleaved the same testosterone acts. The Bhasin study (NEJM, 1996) is the reference for the dose-dependent anabolic effect.

Study results

What the trials measured

Interactive: switch tabs, tap points, show or hide arms. Arms are named relative to each other, no dosing advice.

Rise after one injection2

Peak compared with baseline, 11 men with hypogonadism

Total testosterone2 peak on days 2 to 5
Cypionate, one injection 3.0-fold
Free testosterone2 peak on days 2 to 3
Cypionate, one injection 4.5-fold
Not bound to SHBG2 peak on days 4 to 5
Cypionate, one injection 6.0-fold
Estradiol2 days 2 to 7
Cypionate, one injection 3.0-fold

Between days 2 and 7 many men were above the normal range, after 13 to 14 days all values were back at baseline. LH was suppressed from the first injection on.

PSA decline of at least half5

Share of men, randomised phase 2 trial with 195 men

Castration-resistant prostate cancer5 monthly dosing against an androgen blocker
Bipolar androgen therapy 28.2%
Androgen blocker (comparison) 25.3%

Time without progression was 5.7 months in both arms. According to the registry cypionate or enanthate was allowed. Bipolar means switching between very high and very low testosterone. Research data from cancer research.

Red muscle model and translucent thigh bone side by side on a bright lab bench, next to sample tubes
Testosterone research applies to all esters. Symbolic image.

Research status

Where the research stands

Registered trials with status, participants and results. As of 26 Oct 2026. 7

  1. Preclinical Pharmacology of testosterone esters
  2. Phase 1 8 trials, 5 completed, 1 stopped early
  3. Phase 2 19 trials, 10 completed
  4. Phase 3 1 trial, 1 completed
  5. Approval since 1978
53 participants in phase 3 Approved: ChEMBL lists Testosterone Cypionate with phase 4 as the highest phase and first approval in 1978.8
Show all 20 phase 2 and 3 trials on a timelineHide timeline 11 completed 9 running 1 with results
Phase 2
Phase 3

Bar: start to primary endpoint (planned for running trials). Green = completed, blue = progress until 26 Oct 2026. Phase 1: 8 trials on safety and pharmacokinetics, not shown as bars.

Side effects

  • Estrogen-related: water retention, gyno risk.
  • Possible hematocrit rise.
  • HPTA suppression - PCT topic.
  • Androgenic: acne, hair loss in predisposed individuals.

Tolerability

Haematocrit above 50 percent by formulation

Out of 100 men per group, how many had their haematocrit rise above 50 percent. Retrospective review, not a randomised trial.

67 of 100 Injection (cypionate or enanthate)
35 of 100 Pellets under the skin
13 of 100 Gel on the skin
Event Injection (cypionate or enanthate)Pellets under the skinGel on the skin
Haematocrit above 50%3 67%35%13%

Abstract values 66.7, 35.1 and 12.8 percent, rounded in the chart. The men on injections were younger and had higher haemoglobin and haematocrit at baseline. No rise in PSA was seen in any group, HDL stayed unchanged.3

Storage

Store the oil solution at room temperature, protected from light - no fridge needed. Out of reach of children.

Four glass vials with golden oil on a white shelf, next to them a folded light blue cloth
Oil solution at room temperature and protected from light, no fridge needed. Symbolic image.

Related

Related compounds

Same receptors or blends with Testosterone Cypionate: all in the TPD lexicon.

Testosterone Cypionate
Testosterone Enanthate Long ester, practically the same Testosterone Propionate Short ester, more frequent doses Testosterone Phenylpropionate Medium-length ester Testosterone Decanoate Very long ester Testosterone Undecanoate Ultra-long ester, few injections Tri-Test Contains cypionate plus two more esters

FAQ

Common questions about Testosterone Cypionate

Short answers, each backed by the sources below.

How long does one injection last?

In a study with 11 men the testosterone level tripled on days 2 to 5, free testosterone rose 4.5-fold. Many were above the normal range between days 2 and 7, after 13 to 14 days everything was back at baseline. With an injection every two weeks the levels therefore swung widely between high and low.2

Cypionate or enanthate, what is the difference?

In practice hardly any. The esters differ by one carbon atom, once it is split off the same testosterone acts. Many studies therefore allow both, for example the clinic review on subcutaneous use and the review on haematocrit. Several cancer trials on the registry also allow cypionate or enanthate.437

Is Testosterone Cypionate approved?

Yes. The ChEMBL database lists Testosterone Cypionate as an approved drug with first approval in 1978. Trials are still running on ClinicalTrials.gov, mainly on very high testosterone levels in prostate cancer. Everything here is the state of research, not a recommendation.87

Does subcutaneous work too?

In a clinic review of 63 people injecting cypionate or enanthate under the skin weekly, all reached normal male levels. All 22 who had injected into the muscle before preferred subcutaneous use. Minor, transient reactions at the injection site occurred in 9 of 63.4

What about haematocrit?

Testosterone stimulates the production of red blood cells. In a three-year review 66.7 percent of men on injections (cypionate or enanthate) had a haematocrit above 50 percent, 35.1 percent on pellets and 12.8 percent on gel. The men on injections were younger and had higher values at baseline. No PSA rise was seen in any group.3

What is bipolar androgen therapy?

A research approach in prostate cancer that switches between very high and very low testosterone. In the randomised TRANSFORMER trial with 195 men time without progression was the same at 5.7 months with monthly testosterone and with an androgen blocker. PSA fell by at least half in 28.2 versus 25.3 percent, side effects were mostly grade 1 to 2. This is cancer research and not a pointer for personal use.5

Which trials are still running?

As of 26 October 2026 eight phase 2 trials with Testosterone Cypionate are recruiting on the registry, all on prostate cancer. Two more are running without new participants, one of them on the pelvic floor in postmenopausal women.7

Glossary

Terms explained briefly

Dotted words in the text open these explanations directly.

Androgen receptor
Protein inside the cell that testosterone binds to. Genes are then read, for example for muscle building.
Aromatase
Enzyme that converts part of the testosterone into estradiol.
Bipolar androgen therapy
Research approach in prostate cancer: alternating very high and very low testosterone.
Erythropoiesis
Production of red blood cells in the bone marrow. Testosterone stimulates it.
Ester
An attached acid chain. It makes testosterone oil-soluble and sets how slowly it is released from the depot. It is split off in the blood.
Estradiol
The main oestrogen. In men it is also made from testosterone and rises with the testosterone level.
Haematocrit
Share of red blood cells in the blood. If it rises a lot, the blood gets thicker.
Hormone axis (HPTA)
Hypothalamus, pituitary and testes together control the body's own testosterone production. Testosterone from outside suppresses this axis.
Intramuscular
Into the muscle, for example the glute or thigh.
SHBG and free testosterone
SHBG is a carrier protein in the blood that binds testosterone tightly. Only the free or loosely bound part acts directly.
Subcutaneous
Into the fat layer just under the skin.
Trial phases
Phase 1 tests tolerability in a few people, phase 2 looks for the dose, phase 3 confirms benefit and safety in many. Phase 4 runs after approval.

Practice

PCT / after coming off

Anabolic substances suppress the body's own testosterone production in the research context. Anyone who comes off a cycle (rather than running it continuously) typically uses a post-cycle therapy (PCT) to restart the natural axis (HPTA).

The standard scheme in the research/literature context combines a SERM (tamoxifen and/or clomifene, alternatively enclomiphene) over roughly four weeks, optionally preceded by HCG to re-sensitise the testes before the SERM block. An aromatase inhibitor (anastrozole/exemestane) belongs more to on-cycle estrogen control than to the PCT itself.

Tip: order the PCT items together with the cycle so they are already on hand when you come off.

This information serves research and educational purposes only. Not medical advice.

Tamoxifen (Nolvadex) SERM, core of PCT View Clomid (Clomifen) SERM, core of PCT View Enclomiphene (Androxal) SERM alternative View HCG testicular restart before PCT View Arimidex (Anastrozole) aromatase inhibitor, on-cycle View Aromasin (Exemestane) aromatase inhibitor, on-cycle View

Evidence

Sources

Show all 8 sourcesHide sources 6 Studies1 Trial registry1 Database checked 26 Oct 2026

Studies

  1. Supraphysiologic testosterone doses, muscle size and strength in healthy men

    Bhasin et al., New England Journal of Medicine, 1996

    DOI 10.1056/NEJM199607043350101 PMID 8637535
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  2. Hormone kinetics after one injection

    Nankin, Fertility and Sterility, 1987

    DOI 10.1016/s0015-0282(16)59237-1 PMID 3595893
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed (Titel und Seiten, Datensatz ohne DOI)
  3. Gel, injection and pellets compared over 3 years

    Pastuszak et al., Sexual Medicine, 2015

    DOI 10.1002/sm2.76 PMID 26468380
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  4. Subcutaneous instead of intramuscular, clinic review

    Spratt et al., Journal of Clinical Endocrinology and Metabolism, 2017

    DOI 10.1210/jc.2017-00359 PMID 28379417
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  5. TRANSFORMER: bipolar androgen therapy versus androgen blocker

    Denmeade et al., Journal of Clinical Oncology, 2021

    DOI 10.1200/JCO.20.02759 PMID 33617303 NCT02286921
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  6. Pharmacology of anabolic steroids, review

    Kicman, British Journal of Pharmacology, 2008

    DOI 10.1038/bjp.2008.165 PMID 18500378
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed

Trial registry

  1. All trials on ClinicalTrials.gov

    ClinicalTrials.gov, U.S. National Library of Medicine

    Checked 26 Oct 2026 via ClinicalTrials.gov API v2

Database

  1. Mechanism and approval in ChEMBL

    ChEMBL, EMBL-EBI (CHEMBL1201101)

    Checked 26 Oct 2026 via ChEMBL

In the shop

Testosterone Cypionate in the catalog

Sizes, prices and shipping times are on the product page.

To the product