What it is
A long-acting esterified form of testosterone suspended in oil. It is the most commonly prescribed injectable testosterone in the United States.
How it works
After intramuscular or subcutaneous injection, the cypionate ester is gradually cleaved by serum esterases, releasing free testosterone which binds to androgen receptors.
Where it's used
Used in hormone replacement therapy for men with primary or hypogonadotropic hypogonadism.
FDA-approved use
Replacement therapy in males with conditions associated with deficiency or absence of endogenous testosterone (primary and hypogonadotropic hypogonadism).
Tracking it
Testosterone Cypionate is injectable, so two things matter in a log: when you dosed and where. Rotating sites and writing both down prevents the classic “did I already pin the left side?” problem. with a half-life of about 8 days (192 h), a dose log also lets a tracker model the relative amount still in your system between doses.
Source
OpenFDA
Last reviewed 2026-06-11