Most tirzepatide, the active ingredient in Mounjaro, is eliminated within roughly 30 days of the last dose, although timing varies. Its half-life of around five days allows one injection a week. Semaglutide, in Ozempic and Wegovy, has a half-life of around one week; its labels give five to seven weeks after the last dose. Decisions about a pregnancy, a procedure or a switch follow the guidance for each medication and an individual clinical assessment, not the half-life alone.
- After each half-life, the amount of a medication left in the blood falls by half, so a medication with a long half-life leaves the body gradually.
- The US Zepbound label puts the half-life of tirzepatide at five to six days for people living with overweight or obesity, close to the five days in the Mounjaro label.
- The Ozempic and Rybelsus labels state that semaglutide is present in the circulation for around five weeks after the last dose.
- The Wegovy label gives the longest range, five to seven weeks, counted from a final 2.4 mg injection or a final 25 mg tablet.
- Foundayo is a once-daily tablet with a half-life of around 29 to 49 hours, and its prescribing information gives no time for it to leave the body.
- The MHRA advises stopping semaglutide at least two months, and tirzepatide at least one month, before trying to conceive.
- The Mounjaro prescribing information asks patients to tell their doctors before any planned procedure, because of the risk of aspiration under anaesthesia.
How long Mounjaro stays in your system after the last dose
Lilly’s medical information gives a period of around 30 days after the last dose for tirzepatide, the active ingredient in Mounjaro. Most tirzepatide is eliminated within roughly 30 days of the last dose, although timing varies. Lilly is the company that makes Mounjaro.
The Mounjaro prescribing information gives tirzepatide a half-life of around five days. The Zepbound label, the US prescribing information for tirzepatide in weight management, gives five to six days in people with overweight or obesity. Our page on tirzepatide explains how the medication acts on appetite and blood sugar.
What is a half-life?
A half-life is the time it takes for the level of a medication in the blood to fall by half. Over the next half-life, the level halves again, so the medication leaves the body gradually over several half-lives.
With a half-life of around five days, some of each weekly Mounjaro dose is still in the body when the next dose is due. This is what allows tirzepatide, and semaglutide given as an injection, to be taken once a week. Our article on how long weight loss injections take to work covers the first weeks of treatment.
How long do Wegovy, Ozempic and Foundayo stay in the body?
Each prescribing information gives a half-life, and some also state how long the medication remains in the body after the last dose. The table below gives each source’s own statement, with no figure added where a source gives none.
| Medication | Active ingredient | Half-life | Time in the body after the last dose, as the source states |
|---|---|---|---|
| Mounjaro | Tirzepatide | Around 5 days | Cleared in around 30 days (Lilly medical information) |
| Ozempic (type 2 diabetes) | Semaglutide | Around 1 week | Present in the circulation for around 5 weeks (Ozempic prescribing information) |
| Wegovy injection and Wegovy pill | Semaglutide | Around 1 week | Around 5 to 7 weeks after the last 2.4 mg injection or 25 mg tablet (Wegovy prescribing information) |
| Rybelsus (type 2 diabetes) | Semaglutide | Around 1 week | Present for around 5 weeks (Rybelsus prescribing information) |
| Foundayo | Orforglipron | Around 29 to 49 hours | Not stated in the prescribing information |
The semaglutide medications share an active ingredient and a half-life of around one week, so their times in the body are similar. The Ozempic prescribing information and the Rybelsus prescribing information both give around five weeks, and the Wegovy prescribing information gives the longest range. Our page on semaglutide explains how the Wegovy pill, Ozempic and Rybelsus differ.
Foundayo is taken as one tablet a day, and the Foundayo prescribing information puts its half-life at around 29 to 49 hours. Its label gives no time for the body to clear it after the last dose.
Planning a pregnancy after Mounjaro or semaglutide
The MHRA, the UK medicines regulator, advises stopping semaglutide (Wegovy, Ozempic, Rybelsus) at least two months before trying to conceive, and tirzepatide (Mounjaro) at least one month before. The NHS guidance on tirzepatide advises stopping it at least four weeks before you start trying for a pregnancy. The Ozempic and Wegovy prescribing information also advise stopping at least two months before a planned pregnancy.
Foundayo should not be used during pregnancy because it may harm an unborn baby. Breastfeeding is also not recommended while taking Foundayo.
If you take oral contraceptives, the Mounjaro prescribing information advises a non-oral method or an added barrier method for four weeks after starting and after each dose increase. If you are planning a pregnancy, your endocrinologist will agree the timing of your last dose with you.
Surgery and procedures while taking a GLP-1 medication
Before any planned surgery or procedure, your doctor and your anaesthetist need to know that you take a GLP-1 medication. The MHRA advises telling the anaesthetist, and the Mounjaro label gives the reason: a risk of pulmonary aspiration, when stomach contents enter the lungs, under anaesthesia.
Because an injected GLP-1 medication stays in the body for weeks after the last dose, the plan for your doses is agreed in advance. Your surgical team and your endocrinologist will advise you on what to do with your doses before the procedure.
Appetite after the last dose of a GLP-1 medication
As the level of the medication falls after the last dose, its effect on appetite may also fade. Harvard Health Publishing notes that many people feel hungry sooner after meals and think about food more often after stopping a GLP-1 medication.
Some patients regain weight after stopping. If your weight starts rising after treatment stops, contact your endocrinologist early. They can review your lifestyle plan and whether further treatment is appropriate.
Our articles on what happens when you stop taking Mounjaro, Ozempic or Foundayo and maintaining weight loss after GLP-1 treatment cover this in more detail.
Stopping or switching GLP-1 medications with your endocrinologist
When it is time to come off the medication, your endocrinologist will help plan whether and how to stop treatment and what support you will need afterwards. No single evidence-based schedule for stopping exists. Our article on stopping a weight loss injection safely explains the options.
If you take a GLP-1 medication for type 2 diabetes, stopping it can worsen blood sugar control. Your endocrinologist will plan any change in treatment with you.
If you are switching from one GLP-1 medication to another, your endocrinologist will plan when the new medication starts. The first medication remains in the body for some time after the last dose. The Foundayo prescribing information advises against taking Foundayo with another GLP-1 medication.
Frequently asked questions
Does Mounjaro wear off by the end of the week?
Not completely. The level of tirzepatide falls during the week, but the next injection is due before the previous dose has left the body. Your endocrinologist can review any change in appetite towards the end of the week at your monthly follow-up.
How long does 2.5 mg Mounjaro stay in your system?
Lilly gives one figure for Mounjaro, around 30 days after the last dose, with no separate time for the 2.5 mg starting dose. The half-life in the prescribing information is also a single figure, around five days. Our Mounjaro dosage guide explains the starting dose and each step.
Can you stop Mounjaro suddenly?
We recommend agreeing a plan with your endocrinologist first. A sudden stop does not remove the medication from the body at once, and appetite may return as the level falls. If you take Mounjaro for type 2 diabetes, your endocrinologist will also plan how your blood sugar is managed.
Does Foundayo leave the body faster than the injections?
Its half-life is shorter. Foundayo’s half-life is around 29 to 49 hours, against around five days for tirzepatide and around one week for semaglutide. The label does not state how long Foundayo stays in the body after the last dose.
Patients should not decide by themselves to start a GLP-1 medication. A doctor’s review is critical to ensure the treatment is safe and appropriate for the individual.
At our Dubai clinic, your endocrinologist will assess you, review your treatment and plan any pause, stop or switch with you. You can book a weight loss consultation on +971 4 285 3885 or send us a message on WhatsApp.
