Peptide half-life & active-level calculator

See how a compound accumulates to steady state at your dose and schedule — the estimated active amount over time, plus peak and trough once it levels off.

What half-life means for your protocol

A compound's half-life is how long it takes for half of it to clear. Each dose stacks on what's left of the previous ones, so levels climb until what you take each interval equals what you clear — that plateau is steady state, reached after roughly five half-lives.

This is why a long-half-life GLP-1 like semaglutide or retatrutide feels different at week 4 than week 1 — it's still building. Short-half-life peptides clear between doses, so their curve spikes and falls rather than plateauing high.

Open the calculator (needs JavaScript). Estimates from published half-lives, not measurements — not medical advice.