About a month. The Zepbound label puts tirzepatide’s elimination half-life at 5 to 6 days [2]. Five half-lives, the rule of thumb for a drug being cleared, comes to 25 to 30 days. By then about 3% of the last dose remains. A review of preconception planning puts the tirzepatide washout at 25 to 35 days [4].
The same numbers apply to Mounjaro, which is the same molecule under a different label. What follows is how long the drug itself lasts. How long its effect on weight lasts after stopping is a separate question, answered by a withdrawal trial in what happens when you stop tirzepatide.
Where the five-day figure comes from
Eli Lilly’s population model pooled 19 studies and described tirzepatide with a two-compartment model [1]. It put the half-life at about 5 days. The authors found no demographic group that needed a different dose regimen. Both authors are Lilly employees and shareholders.
The label adds the details a patient can use [2]. A dose peaks in the blood at a median of 24 hours, with a range of 8 to 72 hours. Tirzepatide is 99% bound to albumin, which is what keeps it in circulation. Steady-state concentrations were reached after 4 weeks of once-weekly injections.
That last figure is the useful one. Four weeks to build up to a stable level and roughly four weeks to clear out are the same arithmetic run in opposite directions.
What “five half-lives” means in days
Each half-life removes half of what is left. At 5 days, half the last dose remains on day 5, a quarter on day 10, and one eighth on day 15. On day 25 the share is one thirty-second, about 3%. At a 6-day half-life, the same point arrives on day 30.
That is a calculation from the label’s half-life, not a measurement in anyone’s blood. Half-life also varies between people. The label reports clearance with a coefficient of variation of about 20% [2].
What a radiolabel study measured
One study followed a tagged dose directly [3]. Healthy men received a single injection of about 2.9 mg tirzepatide carrying a radioactive label. Most of the excreted dose was recovered within 480 hours, which is 20 days. About 66% came out in urine and 33% in feces.
Intact tirzepatide was not found in urine or feces at all. What leaves the body is broken down first, by cleavage of the peptide chain and oxidation of its fatty-acid side chain. The study used one small dose in healthy men. It did not measure the higher doses used for weight loss.
Does it stay longer with kidney or liver disease?
Not by a clinically relevant amount. In a single-dose study of 45 people given 5 mg, exposure in mild, severe and dialysis-dependent kidney disease matched normal kidneys [5]. Blood was sampled for up to 648 hours, about 27 days. The moderate group ran 25 to 29% higher, and the authors judged no effect clinically relevant.
A matching study in 32 people with liver impairment found exposure and half-life similar to healthy controls [6]. Both studies gave one 5 mg dose, so neither measured repeated weekly dosing. What the evidence shows for people on dialysis more broadly is set out in can you take a GLP-1 on dialysis.
A missed dose
The label’s rule follows from the half-life [2]. Take a missed dose as soon as possible within 4 days, or 96 hours. After 4 days, skip it and take the next dose on the usual day. The injection day can move, as long as doses are at least 3 days apart.
The label gives no schedule for restarting after a longer break. That decision belongs to a prescriber. The pattern of nausea at each new dose is covered in how long nausea lasts on a GLP-1.
Oral contraceptives: the 4-week window
The label tells people on the pill to switch to a non-oral method, or add a barrier method [2]. The backup covers 4 weeks after starting Zepbound and 4 weeks after each dose increase. Hormonal methods that are not swallowed should not be affected.
This window is not about how long tirzepatide stays in the body. The cause is slower stomach emptying, which the label says is largest after the first dose and then diminishes. The pharmacokinetic study behind it is read in tirzepatide and oral contraception.
Stopping before conception
The label does not set a washout before trying to conceive. It says to stop Zepbound when a pregnancy is recognized, and calls the human data insufficient to evaluate risk [2]. The concern comes from animal studies, where fetal growth reductions appeared at clinical exposures.
A 2025 narrative review filled that gap with the half-life [4]. It recommends stopping tirzepatide 25 to 35 days before conception, against at least 35 days for semaglutide. That is one author’s synthesis of 9 studies, not a trial result. The human pregnancy data are in GLP-1 drugs in pregnancy, and effects on fertility in do GLP-1 drugs affect fertility.
Breastfeeding
In a single-dose study of 11 lactating women given 5 mg, tirzepatide was undetectable in 164 of 171 milk samples [2]. The amount found in the other 7 was under 0.02% of the dose. The last measurable level appeared 5 days after the injection. Effects on a breastfed infant were not measured.
Stopping before surgery
The label warns that people on these drugs have aspirated stomach contents under anesthesia, despite fasting as instructed [2]. It also states that the data are insufficient to say whether pausing the drug reduces retained stomach contents. That is a month-long washout meeting a question nobody has answered. What one anesthesia study found is in GLP-1 drugs and an empty stomach, and the label tells patients to report the drug before any planned procedure.
Compounded tirzepatide
Every figure here comes from studies of Lilly’s product. Compounded tirzepatide is not FDA-approved, and its pharmacokinetics were not measured in these studies. The molecule is the same, so the half-life would be expected to match. Whether a given compounded product delivers the stated dose is a separate question.