COMPOUND

Compounds / TRT and hormones

Test Cypionate

Testosterone Cypionate (Depo-Testosterone)

TRT and hormones SubQ · IM FDA approved

The North American standard TRT ester. Injectable depot formulation with an 8-day half-life, typically dosed weekly or split twice-weekly for steady serum levels.

At a glance

Half-life
~8 days ~8 days (FDA label). Tmax ~4-5 days post-injection. Once-weekly dosing produces ~3:1 peak/trough; twice-weekly (Q3.5d) flattens it to <2:1.
Routes
SubQ · IM
Evidence base
4 studies 3 human · 1 review

Mechanism

Ester hydrolysis releases free testosterone from the oil depot. Testosterone acts on the androgen receptor in muscle, bone, brain, and skin; peripheral aromatization to estradiol is essential for bone and CNS function (estradiol is not a side effect; it's part of how TRT works).

Dosing

Any amounts shown here are reported from published studies only. 3 of 4 catalogued studies involved human subjects. COMPOUND does not publish its own dosing guidance.

Where a study reports an amount, it appears in that study's entry below, attributed to the source.

Published evidence

  1. Human RCT 2014

    Testosterone induces erythrocytosis via increased erythropoietin and suppressed hepcidin: evidence for a new erythropoietin/hemoglobin set point

    Bachman E, Travison TG, Basaria S, et al. J Gerontol A Biol Sci Med Sci

    Testosterone raises Hb/Hct by stimulating EPO and suppressing hepcidin; IM formulations carry the highest erythrocytosis risk.

    PMID 24158761

  2. Human RCT 2005

    Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression

    Coviello AD, Matsumoto AM, Bremner WJ, et al. J Clin Endocrinol Metab

    HCG 125/250/500 IU EOD maintained intratesticular T at 75%/93%/126% of baseline (-25%/-7%/+26%) vs 6% in TE/placebo controls. 250 IU is the minimum dose to approximate baseline ITT.

    PMID 15713727

  3. Human observational 2022

    Pharmacokinetics of testosterone therapies in relation to diurnal variation of serum testosterone levels as men age

    Pastuszak AW, Gittelman M, Tursi JP, et al. Andrology

    Comparative PK across testosterone esters vs the young-male diurnal rhythm; cypionate Tmax ~4-5d, half-life ~8d; Q3.5-7d dosing flattens peak-trough swings.

    PMID 34510812

  4. Review 2018

    Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline

    Bhasin S, Brito JP, Cunningham GR, et al. J Clin Endocrinol Metab

    Target total T 400-700 ng/dL; measure trough midway between injections; monitor Hct every 3-6 months first year.

    PMID 29562364

Reported side effects

Erythrocytosis / elevated hematocrit
Very common Serious · Up to 40% on IM injectable vs ~10-15% on topical gels. Hold therapy at Hct ≥54%. Screen for untreated sleep apnea (exacerbates risk). Monitor at baseline, 3mo, 6mo, then annually.
Testicular atrophy
Very common Moderate · Near-universal without HCG. Intratesticular testosterone drops ~94% within 3 weeks of starting TRT.
Infertility / azoospermia
Common Serious · Azoospermia develops in many men within 3-6 months. Recovery takes 6-18 months after discontinuation and isn't guaranteed. Mitigation: HCG or enclomiphene; consider sperm banking pre-TRT if fertility matters.
Acne / oily skin
Common Mild · Correlates with testosterone peaks 24-72h post-injection.
E2 elevation symptoms
Common Mild · Water retention, gynecomastia, mood changes, blunted libido when estradiol runs high. Often resolved by splitting injection frequency before adding an aromatase inhibitor. Only ~2.6% of men on TRT actually need AI intervention.

Reconstitution and storage

Injectable oil solution; no reconstitution. Standard concentrations: 100mg/mL and 200mg/mL.

Room temperature (15-30°C / 59-86°F). Do not refrigerate: oil can become viscous. Protect from light. Stable to expiration.

Open the reconstitution calculator for Test Cypionate