How Long GLP-1 Drugs Stay in Your System

A once-weekly injection stays active in your body for a lot longer than a week. Both approved GLP-1 molecules are built with a long elimination half-life specifically so a single weekly dose keeps working until the next one — which also means each drug lingers for weeks after your last injection, not hours.

The actual numbers, from each label

Semaglutide's own FDA-approved prescribing information states its elimination half-life is approximately one week. For Ozempic, the label adds a direct clearance estimate: semaglutide "will be present in the circulation for about 5 weeks after the last dose." Wegovy's label — same molecule, higher maintenance dose — states a comparable but slightly longer window: "about 5 to 7 weeks after the last dose of 2.4 mg."

Tirzepatide clears somewhat faster. Mounjaro's label states an elimination half-life of approximately 5 days. Zepbound's label — same molecule — states approximately 5 to 6 days, essentially the same figure with a slightly wider range reported. Using the standard rule of thumb that a drug is considered fully cleared after roughly five half-lives, that puts full tirzepatide clearance at somewhere around 25 to 30 days — noticeably shorter than semaglutide's roughly five-to-seven-week window, even though the two molecules are dosed on the same weekly schedule.

Why it matters for surgery

Anesthesia teams care about this because a drug's activity — including its effect on gastric emptying — doesn't switch off the moment you stop taking it. If a procedure is scheduled and your team wants to know how recently you've been exposed to a GLP-1 drug, the honest answer accounts for the full clearance window above, not just the number of doses you've skipped. See GLP-1 drugs before surgery for what the actual aspiration-risk evidence shows and why guidance in this area doesn't reduce to a simple "stop N days before" rule.

Why it matters for pregnancy planning

This is the one place a specific number is printed directly on a label rather than left to general clearance math. Wegovy's FDA-approved label states plainly: "Discontinue WEGOVY at least 2 months before a planned pregnancy because of the long half-life of semaglutide." That two-month window is longer than the roughly five-to-seven-week clearance estimate above — a deliberately conservative margin, not the bare minimum clearance time. If pregnancy is a possibility while on any GLP-1 drug, this is a conversation to have directly with your prescriber well ahead of trying to conceive, not something to time on your own from a clearance estimate.

Why it matters for switching drugs or providers

Because both molecules stay active for weeks, not days, switching from one GLP-1 drug to another — or between providers carrying different molecules — isn't usually an instant reset. Overlapping exposure is possible if a new prescription starts before the old one has meaningfully cleared, which is one more reason to disclose your full GLP-1 history to any new provider rather than treating it as old news the moment you stop refilling. If cost or supply is the reason you're considering GLP-1 microdosing as a bridge between prescriptions, that's a use case with no trial evidence behind it either way — worth reading before, not after.

The practical takeaway

Treat "I stopped taking it" and "it's out of my system" as two different milestones, separated by roughly a month for tirzepatide and closer to a month and a half for semaglutide. That gap is exactly why the trial evidence on GLP-1 weight regain after stopping shows appetite changes creeping in gradually rather than the instant the last dose is taken — the drug is still working for weeks after. The full FDA-labeled side-effect and dosing picture for both molecules is in GLP-1 side effects and GLP-1 dosage and titration schedules; the rest of the Desk's sourced evidence is in the research library.