/CALCULATOR
Testosterone
Half-Life Simulator
Models first-order elimination from your injection schedule across 12 weeks. Shows the peak / trough swing for any ester and any cadence. Same math the MyTRT app uses for its PK simulation.
Half-life: 8d
~3.5 days between injections
70.0 mg per injection
/HOW_IT_WORKS
Injected testosterone follows first-order pharmacokinetics: a fixed fraction of what's left decays per unit time. The concentration at any moment is the sum of contributions from every prior injection, each decayed by its time-since-dose.
Formally: C(t) = Σ Dose × e^(−k × Δt), where k = ln(2) / half-life. The simulation here uses the same model — what changes between protocols is the half-life of the ester and the spacing/dose of the injections.
/COMMON_HALF_LIVES
Half-lives are population averages — individual variability is significant. Use the simulation as a planning tool, not a clinical predictor.
/STEADY_STATE
Steady state — where the amount entering your system per dose equals the amount eliminated between doses — is reached after roughly 4–5 half-lives of consistent dosing. For cypionate (8d half-life), that's ~32–40 days. For propionate (2d), it's ~8–10 days.
Before steady state, every successive dose stacks higher than the last. After steady state, peaks and troughs become predictable and stable. Most lab draws should happen after steady state has been reached on the current protocol — otherwise you're measuring a moving target.