Testosterone Cypionate: The US Depot Standard, Examined

Two esters dominate injectable testosterone history: enanthate in Europe, cypionate in the United States. Same hormone, slightly different clock.

The molecule

Testosterone cypionate (C₂₇H₄₀O₃, ≈412.6 g/mol) is unmodified testosterone behind a cyclic ester — fully aromatizable, fully 5α-reducible, exactly the molecule the body makes, just released over days instead of hours. In the ester master reference it sits at ≈8 days half-life, between enanthate and the two-week undecylenate/decanoate tier; the clearance calculator and half-life plotter turn any starting point into a decay curve.

The enanthate-versus-cypionate question is answered in depth in our comparison article; the short version is that meta-analytic PK work finds small, not zero, differences in time-to-steady-state and peak flatness.

Research context

Cypionate is the reference testosterone in much of the older depot-endocrinology literature — the 1950s–80s testosterone-replacement trials that shaped dosing schedules used it, so reproducing or citing those curves requires the same ester. It is also the baseline arm in aromatase, 5α-reduction and SHBG-binding models where “plain testosterone kinetics over a week” is the control condition.

Practical notes

200 mg/mL oil solution, 10 mL vials — no reconstitution. CAS and documentation on Testosterone Cypionate; the four-ester hybrid lives in Sustanon 250.

References: Kicman A.T., “Pharmacology of Anabolic-Androgenic Steroids.” Handbook of Experimental Pharmacology, 2008 · Schulz & Nygaard, long-acting testosterone preparations, Acta Pharmacol Toxicol, 1980s depot comparisons.

For laboratory research use only. Not medical advice.