How long it stays in your system

The label numbers

Semaglutide (Wegovy, Ozempic): half-life about 1 week. The Wegovy label says it "will be present in the circulation for about 5 to 7 weeks after the last" injection of 2.4 or 7.2 mg, or the last 25 mg tablet.^[1] Tirzepatide (Zepbound, Mounjaro): half-life about 5 days, or 5 to 6 days in people with obesity.^[2]

A half-life is the time for the amount in the blood to fall by half. A common rule of thumb in pharmacology is that a drug is mostly gone after about five half-lives, which for tirzepatide is roughly 25 days. That is our arithmetic, not a label statement.

What that means

After a last dose, appetite effects and side effects fade gradually. In the withdrawal trials, people switched to placebo regained weight steadily: 6.9% over 48 weeks in STEP 4 and 14.0% over 52 weeks in SURMOUNT-4; see what happens when you stop.^[3][4]

Why it matters for planning

• Pregnancy: the long half-life is the reason the Wegovy label says to stop at least 2 months before a planned pregnancy.^[1] See pregnancy and birth control.
• Surgery: the drug is still active for weeks, which is part of the anaesthesia discussion. See surgery.
• Missed doses: the labels have specific rules for missed doses and restarting after a gap; they are dosing instructions, so ask your prescriber or pharmacist rather than guessing.^[1][2]

The short version

Questions to bring to your prescriber

Print these or screenshot them. They are conversation starters, not a checklist of things to do.

• If I stop, when would you expect appetite to come back, and what is our plan for that?
• I missed a dose: what does my label say I should do?
• If I have a gap of several weeks, do I need to restart at a lower dose?

Sources

Every number on this page traces to one of these. "Primary read" means the full paper or label was read; "abstract only" means only the abstract was available; "secondary" means the figure was taken from a named review.

1. Novo Nordisk / FDA. Wegovy (semaglutide) injection and tablets, prescribing information, revised 06/2026. label
2. Eli Lilly / FDA. Zepbound (tirzepatide) prescribing information, revised 08/2026. label
3. Rubino D et al. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance (STEP 4). JAMA 2021;325:1414–25. primary read · RCT · industry-funded
4. Aronne LJ et al. Continued treatment with tirzepatide for maintenance of weight reduction (SURMOUNT-4). JAMA 2024;331:38–48. primary read · RCT · industry-funded

Related explainers

All 35 questions