Half-life and washout by drug
“Half-life” is the time for blood levels to fall by half. A useful rule: after about five half-lives, roughly 97% of a drug is gone — that's the practical “out of your system” point.
| Medication | Half-life | Mostly cleared in |
|---|---|---|
| Semaglutide (Ozempic, Wegovy, Rybelsus) | ~1 week | ~5 weeks |
| Tirzepatide (Mounjaro, Zepbound) | ~5 days | ~3.5–4 weeks |
| Dulaglutide (Trulicity) | ~5 days | ~3–4 weeks |
| Liraglutide (Victoza, Saxenda) | ~13 hours | ~3 days |
| Exenatide IR (Byetta) † | ~2.4 hours | ~12–24 hours |
† Byetta and Bydureon BCise were discontinued in the US in October 2024 — a business decision, not a safety recall. Note the extended-release form (Bydureon BCise) had a much longer effective half-life (~2 weeks), so it cleared over roughly 10 weeks, not the ~1 day shown for the immediate-release figure above. Half-lives are from the manufacturers' prescribing information; individual clearance varies with kidney/liver function and other factors.
Why the long tail matters
Because semaglutide and tirzepatide linger for weeks, two things follow. First, effects — both the appetite suppression and any side effects — fade gradually after your last dose rather than stopping abruptly. Second, appetite (and often weight) tends to return over the following weeks as levels fall, which is why stopping is a planned decision, not a light switch.
Surgery and anesthesia — the current guidance
This changed — don't rely on old advice. In 2023 the ASA suggested routinely holding GLP-1s before procedures (day-of for daily, one week for weekly). That was superseded by multisociety guidance in October 2024.
Under the current guidance, most patients can continue their GLP-1 through surgery. For higher-risk cases — weekly dosing at higher or recently escalated doses, or prominent GI symptoms — the decision is individualized; if the drug is held, a weekly formulation is typically held about one week before. A 24-hour clear-liquid diet the day before can reduce aspiration risk either way.
Your surgical and anesthesia team makes the final call for your specific procedure — always follow their instructions and tell them you take a GLP-1.
Pregnancy planning
Because of the long half-life, the label advises discontinuing semaglutide at least about two months beforea planned pregnancy, so it clears before conception. GLP-1 medications are not established as safe in pregnancy and animal studies show harm. If you're planning a pregnancy — or might already be pregnant — talk to your prescriber about stopping and about alternatives.
Half-lives are population averages; your own clearance depends on kidney and liver function, dose, and how long you've been on the drug. This page is educational, dated 2026-07-17, and not a substitute for your prescriber or surgical team.