Tirzepatide, the drug in Mounjaro and Zepbound, has an elimination half-life of about 5 to 6 days. That means the amount in your blood falls by half about every 5 days. By roughly 4 to 5 weeks after your last shot, very little is left. This guide goes through the numbers from the FDA label and explains what they mean for peak time, missed doses and stopping.
One note on sources: Mounjaro and Zepbound contain the same drug. The figures here come from the Zepbound prescribing information, and where we do our own arithmetic we say so.
The Zepbound label says the elimination half-life is approximately 5 to 6 days in people with overweight or obesity. Another section of the label, on overdose, rounds it to "approximately 5 days" (Zepbound label, 12.3 and 10). The label also reports an apparent clearance of about 0.06 L/h, and that tirzepatide is 99% bound to albumin in blood. That tight binding is a big part of why it lasts so long.
The label adds that kidney problems and liver problems did not change how the body handles tirzepatide in its studies, and that age, sex, race and body weight had no clinically relevant effect.
The label gives a half-life but no washout time. So here is the standard shortcut: after 5 half-lives, about 97% of a dose has cleared. With a 5-day half-life that is about 25 days. With a 6-day half-life it is about 30 days. Treat this as a calculation, not a promise. Individual people vary.
| Half-lives passed | Time (5-day half-life) | Share left |
|---|---|---|
| 0 | Peak, about day 1 | 100% |
| 1 | 5 days later | 50% |
| 2 | 10 days later | 25% |
| 3 | 15 days later | 12.5% |
| 4 | 20 days later | 6.3% |
| 5 | 25 days later | 3.1% |
This table assumes a single dose and starts from the peak. In real life, if you have been on tirzepatide for months, you start from your steady-state level, so the same shape begins higher. Add a week or so if you want a safety margin when you plan around a procedure, and ask your care team.
For comparison, the Wegovy label says that with a half-life of about 1 week, semaglutide stays in the blood for about 5 to 7 weeks after the last injection (Wegovy label, 12.3). Tirzepatide's shorter half-life points to a somewhat shorter tail, but the Zepbound label does not give a number.
After an injection under the skin, the median time to the highest blood level is 24 hours, with a range of 8 to 72 hours. Absolute bioavailability, meaning the share that reaches the blood, is 80%. The label says exposure was similar whether people injected in the abdomen, thigh or upper arm (Zepbound label, 12.3).
So the day after your shot is usually when the level is highest, and the level then slides down over the rest of the week. Because the half-life is shorter than 7 days, roughly 40% of the peak is still there when the next dose arrives.
Each weekly dose adds to what is left from the last one. The label says steady-state levels were reached after 4 weeks of once-weekly dosing, and that exposure goes up in proportion to the dose (Zepbound label, 12.3).
A quick calculation shows the size of the build-up. With a 5-day half-life and a 7-day dosing gap, about 38% of each dose remains when the next one is taken. Adding that up over many weeks gives a level at steady state of roughly 1.6 times what a single dose reaches. With a 6-day half-life it is closer to 1.8 times. This is our arithmetic, not a label figure.
The label also says the slowing of stomach emptying is largest after the first dose and fades over time. The contraceptive advice below is tied to the same effect: it applies after the first dose and after each dose increase.
The label rules are simple (Zepbound label, 2.3):
The long half-life is why a late dose is forgiving. A day or two of delay barely changes the curve. Missing several weeks in a row is different, so call your prescriber about how to restart rather than guessing.
Dose Track estimates your tirzepatide level from the doses you log, so you can see steady state build, a late dose show up as a dip, and the tail after your last shot. It also records the injection site so you can rotate. See the GLP-1 tracking guide. For a side-by-side with semaglutide, read Ozempic vs Mounjaro, or check how long Ozempic stays in your system.
This article is general information, not medical advice. Talk to your prescriber before you start, change or stop any medicine.