How Long Semaglutide and Tirzepatide Stay in Your System After the Last Dose

If you stop semaglutide (Ozempic, Wegovy) or tirzepatide (Mounjaro, Zepbound), the drug does not leave the day your next injection would have been due: it fades over several weeks. The short answer: semaglutide takes roughly five weeks to be practically cleared, and tirzepatide roughly four to five weeks, because their elimination half-lives are about one week and about five days respectively. To watch that washout curve for either figure, plug the half-life into the Peptide Half-Life Visualizer, which reports exactly when you cross 50%, 25%, 10%, and 1% remaining.

Start with the half-lives from the labels

Washout math only works if the half-life is right, so take it from the source. According to FDA prescribing information and clinical pharmacology data:

Drug	Elimination half-life	Basis
Semaglutide	~1 week (≈149–165 hours)	FDA label; albumin-bound, once-weekly dosing
Tirzepatide	~5 days	FDA label; ~99% albumin-bound, once-weekly dosing

Both are long because both are engineered to bind albumin, the slow-turnover blood protein, the mechanism explained in why engineered GLP-1 drugs last a week. Semaglutide’s own label notes it stays in the circulation for about five weeks after the last dose, which is exactly what a one-week half-life predicts.

The washout curve, step by step

Because clearance follows first-order (exponential) kinetics, each half-life removes half of whatever remains. Applying that to each drug from a single “last dose” starting point:

Semaglutide (~1-week half-life):

Time after last dose	Approx. remaining
1 week	50%
2 weeks	25%
3 weeks	~12%
4 weeks	~6%
5 weeks	~3%

Tirzepatide (~5-day half-life):

Time after last dose	Approx. remaining
5 days	50%
10 days	25%
~17 days	~10%
20 days	~6%
~25 days	~3%

The pattern to notice: levels fall fastest at the beginning. In the first week, half of the semaglutide is gone. But the tail is long and shallow: that stubborn last few percent is why the drug is still measurable more than a month out. This is the same exponential shape behind the 5 half-lives rule, which is where “about five weeks” and “about four to five weeks” come from: five half-lives leaves only ~3% and is the standard “practically gone” threshold.

Two important caveats

A single injection is not the same as steady state. The tables above trace one dose. If you have been dosing weekly for a couple of months, the drug has accumulated to steady state, so the amount on board when you stop is higher than one injection’s worth: the last dose sits on top of the tails of previous ones. Clearance still follows the same half-life clock, but you are counting down from a higher starting point. The Dose Interval Visualizer shows how repeated weekly doses build up, which is the level you’d be washing out from.

Half-life describes the blood, not the effect. “Practically cleared” means the drug is nearly gone from circulation; it does not mean appetite and metabolic effects switch off on the same schedule, nor that they linger indefinitely. The relationship between drug levels and lasting effect is its own topic, covered in half-life vs duration of action. What happens to weight and appetite after stopping is covered separately in what happens when you stop a GLP-1.

Why people ask this question

Practical reasons to want a washout estimate include planning around surgery, considering pregnancy, switching between agents, or understanding why side effects may take weeks to fully settle after stopping. In each case the reasoning is the same: count half-lives from the last dose.

• Switching semaglutide to tirzepatide (or back) overlaps two long tails; prescribers plan the timing around it, and we discuss the dose logic in switching semaglutide to tirzepatide.
• Around procedures, the long half-life is why guidance about holding a GLP-1 exists; see stopping a GLP-1 before surgery.
• Individual variation matters. The half-lives above are population averages. Kidney and liver function, body size, and other factors can shift your personal clearance, so treat “five weeks” as an estimate, not a stopwatch.

None of these are decisions to make from a calculator. They are reasons to talk to the clinician who prescribed the drug.

The takeaway

Semaglutide and tirzepatide linger for weeks after the last dose because they are built to. With a one-week half-life, semaglutide is roughly halved in seven days and practically cleared by about five weeks; with a five-day half-life, tirzepatide washes out somewhat faster, over roughly four to five weeks. The curve falls fastest early and trails off slowly, which is why the drug is still detectable long after it “should” feel gone. And remember that clearing the blood is not the same as switching off the effect.

Model either washout in the Peptide Half-Life Visualizer, and use the Dose Interval Visualizer to see the steady-state level you’d be starting from.

This article is educational information about pharmacokinetics, not medical advice. Do not start, stop, switch, or time any GLP-1 medication based on this page; those are decisions for you and your prescriber.

Sources

• OZEMPIC (semaglutide) Prescribing Information — FDA
• ZEPBOUND (tirzepatide) Prescribing Information — FDA
• Tirzepatide — StatPearls, NCBI Bookshelf