Education · not medical advice
GLP-1 half-life: how long these medications actually last
Semaglutide’s half-life is about a week. That single number explains weekly dosing, why levels take a month to plateau, and why one late shot barely moves the needle.
What “half-life” actually means
A drug’s half-life (t½) is the time it takes for the amount in your body to fall by half. It is a property of the molecule, not of you — but it is what determines how often a medication has to be taken, and how long it lingers after the last dose.
After one half-life, ~50% of a dose remains. After two, ~25%. After five, under 4% — which is why about five half-lives is the usual rule of thumb both for a drug washing out and for repeated doses reaching a stable level.
Half-life of each GLP-1 and incretin medication
Population averages from published pharmacokinetic studies and regulatory labels. Individual values vary; every figure links to its source.
| Medication | Half-life (t½) | Time to peak | Dosing | Steady state | Source |
|---|---|---|---|---|---|
| SemaglutideOzempic, Wegovy | ~168 h(~7 days) | 24–72 h | Weekly | ~35 days | Ozempic FDA label (DailyMed) |
| RetatrutideIn clinical trials — not an approved medicine | ~144 h(~6 days) | 12–48 h | Weekly | ~30 days | Urva et al., Lancet 2022;400:1869–81 (PMID 36354040) |
| TirzepatideMounjaro, Zepbound | ~120 h(~5 days) | 24 h(median) | Weekly | ~25 days | Mounjaro FDA label (DailyMed) |
| DulaglutideTrulicity | ~120 h(~5 days) | 48 h(median) | Weekly | ~25 days | Trulicity FDA label (DailyMed) |
| OrforglipronFoundayo | ~29–49 h | 4–8 h | Daily | ~6–10 days | Foundayo (orforglipron) FDA label (DailyMed) |
| Semaglutide (oral)Rybelsus | ~168 h(~7 days) | ~1 h | Daily | ~35 days | Rybelsus FDA label (DailyMed) |
| LiraglutideVictoza, Saxenda | ~13 h | 8–12 h | Daily | ~3 days | Victoza FDA label (DailyMed) |
“Steady state” is roughly five half-lives — the point where the amount going in each week and the amount clearing out roughly balance. Where a study reports a range rather than a single figure, the range is shown. Rows marked “in clinical trials” are not approved medicines anywhere and cannot be prescribed. All values are estimates from published averages, not a measurement of you.
Why weekly dosing works
With a half-life near 7 days, semaglutide never fully clears between weekly injections — each dose lands on top of what is left of the last one. Levels climb for roughly 35 days before flattening out.
- It accumulates. Weekly levels stack until intake and clearance balance.
- It plateaus. Once at steady state, week-to-week levels look flat rather than spiky.
- It fades slowly. After a last dose, meaningful amounts remain for weeks.
What a late or missed dose does
Tirzepatide’s half-life is about 5 days, so steady state takes roughly 25 days. A dose taken a day or two late moves the curve far less than most people expect — the long half-life is doing the smoothing.
What to do about a missed or late dose is a question for the label and your prescriber — this page describes the pharmacology, it does not tell you when to inject.
Common questions
How long does semaglutide stay in your system?
Semaglutide’s published half-life is about 168 hours (7 days), so roughly five half-lives — about five weeks — pass before the great majority of a final dose has cleared. That is a population average from published pharmacokinetics, not a measurement of any individual.
What is the half-life of tirzepatide?
About 120 hours (5 days) for the subcutaneous injection, with peak concentration around 24 hours after a dose. Steady state is reached in roughly 25 days of weekly dosing.
Is there a half-life calculator?
The arithmetic is simple: after each half-life, half of what remains is gone. This page lists the published half-life for each medication so you can work out roughly how much of a dose is left after a given number of days. The Glipath app draws the same curve continuously from your own logged doses.
Why does it take weeks to feel a dose change?
Because levels do not jump to a new plateau immediately. After a dose increase, it takes about five half-lives — weeks for these medications — for levels to settle at the new steady state.
Does half-life tell me what dose to take?
No. Half-life describes how a molecule behaves in the body on average. It says nothing about what dose is right for you, which is a decision for you and your prescriber using the approved label.
Keep reading
Educational only — not medical advice and not a recommended dose. These are population averages from published pharmacokinetic studies, not a measurement of your body. Always follow your prescriber and the approved label.
Built by the makers of Glipath — the private GLP-1 companion for iPhone.Privacy ·Terms ·Support