Testosterone undecanoate is a long-chain ester of testosterone designed for intramuscular injection. It provides sustained testosterone levels with an extended dosing interval compared to shorter esters.
Testosterone undecanoate delivers exogenous testosterone via a long fatty-acid ester that slows absorption and release from the injection site. Once cleaved, free testosterone binds to androgen receptors throughout the body, promoting anabolism, androgenesis, erythropoiesis, and other classical testosterone effects.
The undecanoate ester is hydrolyzed slowly in muscle, resulting in a peak around 4–7 days and a half-life of approximately 20–21 days. This extended profile allows for less frequent dosing intervals, typically every 3–4 weeks at clinical doses, though some users inject more frequently for stability.
Typical Dose
500–1000 mg every 3–4 weeks (clinical/TRT range); performance users may dose 1000–2000 mg weekly or split into multiple injections
Frequency
Every 3–4 weeks (clinical); weekly or split dosing (performance)
Administration
Intramuscular injection
Half-Life
~20–21 days