Testosterone Cypionate
Test Cyp · TC
Standard US TRT ester with a slightly longer release tail than enanthate. Steady state ~4–5 weeks.
Key takeaways
- The standard US TRT ester — ~8-day half-life, steady state in about 5 weeks.
- Twice-weekly injection smooths peak-to-trough swings and reduces estradiol/hematocrit side effects vs once-weekly.
- Aromatizes to estradiol and 5α-reduces to DHT — trough total/free T, E2, hematocrit, lipids, and PSA are the core monitoring set.
- Complete HPTA suppression follows any non-TRT use — plan PCT before the cycle starts, not after.
Overview
What it is
Testosterone cypionate is the most prescribed injectable testosterone ester in the US, used clinically for hormone replacement therapy (TRT) and off-label as a cycle base. The cypionate ester controls the release rate: once injected into muscle, tissue esterases slowly cleave it, freeing testosterone to bind the androgen receptor and drive protein synthesis, nitrogen retention, and erythropoiesis.
Pharmacokinetics
Its roughly 8-day half-life supports once- or twice-weekly injection, with steady state reached after about 5 weeks. Twice-weekly dosing narrows the peak-to-trough swing, which reduces estradiol and hematocrit side effects compared to the same weekly total injected once.
Harm reduction
It aromatizes to estradiol and 5-alpha-reduces to DHT, so monitoring trough total/free T, estradiol, hematocrit, lipids, and PSA is central. HPTA suppression is complete and rapid, so any non-TRT use needs a structured PCT planned before the cycle starts. It is not hepatotoxic since it bypasses first-pass metabolism.
Reported dosing protocols
Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.
| Use case | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| TRT (clinical) | 75–100 mg weekly (or 150–200 mg q2wk) | IM | 1–2× weekly | Ongoing |
| Performance (community) | 300–600 mg weekly | IM | 2× weekly | 10–16 weeks |
Pharmacokinetic summary
- Model tier
- Linear Regression (sublinear dose)
- Half-life
- 6.9 days
- Cmax
- 964 ng/dL
- Tmax
- 4.5 days
- Bioavailability
- 70%
- Typical dose
- 100–600 mg
Harm reduction
- Aromatizes
- Yes
- DHT derivative
- No
- Injection frequency
- 2×/week
- Bloodwork range
- 300–1000 ng/dL
Frequently asked questions
Cypionate vs enanthate — does it matter?
Barely. Cypionate is one carbon longer on the ester, giving a marginally longer tail (~8 vs ~7 days half-life). Dosing schedules and blood levels are effectively interchangeable; cypionate dominates in the US, enanthate elsewhere.
Why inject twice a week instead of once?
Splitting the weekly dose narrows the peak-to-trough swing. High peaks drive more aromatization to estradiol and larger hematocrit excursions; lower troughs avoid the end-of-week crash. Same weekly milligrams, smoother curve — the plotter shows this directly.
Do you need PCT after testosterone cypionate?
For any non-TRT use, yes. Exogenous testosterone fully suppresses the HPTA within weeks. A structured PCT (typically SERMs, sometimes hCG beforehand) restarts endogenous production after the ester clears — with an ~8-day half-life, that means waiting roughly 2–3 weeks post-last-injection before starting SERMs.
References
- Depo-Testosterone PK studies — Advanced + Linear Regression model.
- Snyder et al., NEJM 2016 — The Testosterone Trials — Largest RCT set on testosterone replacement in older men with low T.
Related articles
Related compounds
Testosterone Enanthate
Long-acting testosterone ester; the most common TRT and cycle base. Reaches steady state in ~5 weeks.
Testosterone Propionate
Short-acting ester with sharp peaks; requires frequent injection. Useful for frontloading.
Testosterone Undecanoate (Castor Oil)
Very long-acting ester (Nebido). Dosed 1000 mg every 10–14 weeks for TRT. NHS standard.
Protocols featuring Testosterone Cypionate
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