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An estimate from the doses and published half-lives, not a blood level. Never change a dose or a schedule because of it: ask your prescriber.
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Mounjaro half-life calculator: tirzepatide levels
Mounjaro's label gives tirzepatide a half-life of about 5 days, which is what allows one shot a week. This page opens the half-life calculator on Mounjaro® at 5 mg, with the six doses on its label, from 2.5 mg to 15 mg. Tell it how many weekly shots you have had and when the last one was. It estimates the tirzepatide in your body now, how it builds up and when it has mostly gone. The figures come from the label, not from a blood sample, and the calculator never proposes a dose.
What does the Mounjaro label say about its half-life?
The Mounjaro prescribing information (§ 12.3) gives tirzepatide an "elimination half-life of approximately 5 days, enabling once-weekly dosing". It also says that "Steady-state plasma tirzepatide concentrations were achieved following 4 weeks of once weekly administration."
So the calculator halves the amount every 120 hours; the main half-life calculator page describes the rest of the model. The doses offered here are the ones in § 2.1 of the label, revised in August 2026:
| Mounjaro dose | On the label |
|---|---|
| 2.5 mg once weekly | The starting dose |
| 5 mg, 7.5 mg, 10 mg, 12.5 mg | Each 2.5 mg higher, after at least 4 weeks on the dose before, if more glycemic control is needed |
| 15 mg once weekly | The maximum for adults |
For children aged 10 and older, the label's maximum is 10 mg. Which dose a person takes, and for how long, is set by their prescriber.
A worked example: 8 shots of 5 mg, counted in half-lives
The doses in this example are illustrative. After 8 weekly shots of 5 mg and no ninth, the calculator estimates the tirzepatide left at each multiple of the 5-day half-life:
| After the last shot | Estimated amount | Share of the peak |
|---|---|---|
| 1 day (about the peak) | 5.68 mg | 100% |
| 5 days | 3.37 mg | 59% |
| 10 days | 1.68 mg | 30% |
| 15 days | 0.84 mg | 15% |
| 20 days | 0.42 mg | 7% |
| 25 days | 0.21 mg | 4% |
| 30 days | 0.11 mg | 2% |
Every 5 days the figure halves: 3.37, then 1.68, then 0.84. The 4-week build-up in the label shows here too. The peak after the eighth shot is almost exactly where it settles if the shots went on.
How long does Mounjaro take to clear?
In that example the amount drops below 10% of its last peak about 18 days after the final shot, and below 3% after about 27 days. Five half-lives make 25 days, the usual rule of thumb for a medicine to be mostly gone, and the curve agrees.
Those days do not depend on the dose. A 15 mg shot leaves three times as much as a 5 mg shot at every point, and it halves on the same 5-day rhythm.
What can this estimate not tell you?
- A laboratory value. The curve uses the label's averages for absorption and clearance, and one body can differ from them.
- How you will feel on a given day. The Mounjaro label does not link a level to appetite, blood sugar or side effects.
- Whether a dose should change. The label's 2.5 mg steps depend on glycemic control, which only the prescriber can judge.
Frequently asked questions
How long does Mounjaro stay in your system?
Tirzepatide's half-life is about 5 days. The calculator puts the amount below 3% of its last peak about 27 days after a final shot, so close to four weeks.
Is Mounjaro the same medicine as Zepbound?
Yes, both are tirzepatide. Their labels cover different conditions and word the half-life slightly differently, which the Zepbound half-life page explains.
Why is Mounjaro taken once a week?
Its label says so directly: the half-life of about 5 days is what enables once-weekly dosing. A medicine that halves in about 13 hours, such as liraglutide, needs a daily dose instead.
Sources
- Mounjaro (tirzepatide) prescribing information, DailyMed: half-life and steady state (§ 12.3); starting dose, 2.5 mg steps and maximum doses (§ 2.1, revised 08/2026).
- Saxenda (liraglutide) prescribing information, DailyMed: liraglutide half-life of approximately 13 hours (§ 12.3).
Published by Petros IT Solutions SRL. Read our editorial policy, and send corrections to office@doseandlose.com.