Half-life
Peptide half-life & washout calculator
How much is left, when it is practically gone, and how long until levels plateau. Every half-life here is cited — and where no human study exists, this tool says so instead of inventing a number.
Step 1 — Pick a compound
Step 2 — Timing
46 compounds carry a cited half-life · 8 are recorded as having no human data at all · the rest we have not researched yet, which is not the same thing.
How this is calculated
First-order elimination from a single compartment: the fraction remaining after time t is 0.5(t ÷ half-life). A drug is conventionally treated as practically cleared after five half-lives, when about 3% remains. Building up follows the mirror image, so levels plateau after roughly four to five half-lives of steady dosing.
This ignores the absorption and distribution phases, so it is least accurate in the hours immediately after a dose. Label half-lives are population means — individuals vary, especially with reduced kidney or liver function. Half-life is also route-dependent: a depot formulation and a plain subcutaneous injection of the same molecule behave nothing alike.
If you are having surgery or sedation, tell the anaesthetist you take a GLP-1 drug regardless of what this page says. Delayed gastric emptying is an aspiration risk, and it is not a cosmetic disclosure.
Frequently asked questions
How long does semaglutide stay in your system?
Semaglutide’s label gives an elimination half-life of approximately one week. Roughly half remains after 7 days, a quarter after 14, and about 3% after 35 days — five half-lives, the point at which a drug is conventionally treated as practically cleared. Because concentrations fall gradually, appetite does not return the day after a missed dose.
What is a drug’s half-life?
The time it takes for the amount of drug in the body to fall by half. Elimination is exponential, so the same fraction disappears in each successive half-life: 50% remains after one, 25% after two, 12.5% after three. It sets both how long a drug lingers and how long it takes to build up.
How long until a GLP-1 reaches steady state?
About four to five half-lives of consistent dosing. For a weekly drug with a one-week half-life that is roughly four to five weeks. This is why side effects experienced in the first week do not predict what happens by week five, and why judging a drug too early judges an incomplete picture.
Does BPC-157 have a known half-life?
No. No human pharmacokinetic study of BPC-157 has been published, so no half-life can honestly be stated for it. Figures circulating online are extrapolations from rodent data or are simply invented. This calculator says so rather than showing a number.
How accurate is this calculator?
It models first-order elimination from a single compartment, which is the standard approximation and is good enough for washout questions. It ignores the absorption and distribution phases, so it is least accurate in the first hours after a dose. Label half-lives are population means; individuals vary, particularly with reduced kidney or liver function.
Educational reference only. Pepperz does not provide medical advice, diagnosis, treatment, prescribing guidance, or dosing recommendations. Nothing here is a reason to start, stop, or change a prescribed medicine.