How Long Does Mounjaro Stay in Your System?
Mounjaro stays in your system for about a month after the last injection. Tirzepatide's half-life is about 5 days per the Mounjaro FDA label, so levels fall below 5% of the steady level in about 3 weeks, with traces lasting a little longer.
From the Mounjaro FDA label · Free, no sign-up
At a glance
- Half-life
- about 5 days
- Peak after a dose
- 8 to 72 hours
- Steady state
- about 4 weeks
- Below 5% after stopping
- about 3 weeks
See your real levels
GlucoPal charts your estimated level from the doses you actually log.
Read the chart as a table
Mounjaro 10 mg, last dose on day 42. Modeled amounts absorbed, not blood levels.
| Timepoint | Estimated amount (mg) | % of steady peak |
|---|---|---|
| Day 0 on treatment | 0.00 | 0.0% |
| Day 1 on treatment | 7.0 | 60.8% |
| Day 2 on treatment | 6.3 | 55.2% |
| Day 3 on treatment | 5.5 | 48.1% |
| Day 7 on treatment | 3.2 | 27.6% |
| Day 14 on treatment | 4.4 | 38.1% |
| Day 21 on treatment | 4.8 | 42.1% |
| Day 28 on treatment | 5.0 | 43.6% |
| Day 35 on treatment | 5.1 | 44.1% |
| Day 42, last dose | 5.1 | 44.4% |
| 1 day after the last dose | 11.4 | 99.4% |
| 2 days after the last dose | 10.2 | 88.8% |
| 3 days after the last dose | 8.9 | 77.4% |
| 7 days after the last dose | 5.1 | 44.4% |
| 14 days after the last dose | 1.9 | 16.8% |
| 21 days after the last dose | 0.73 | 6.4% |
| 28 days after the last dose | 0.28 | 2.4% |
Educational estimate, not a blood level or medical advice. Follow your prescriber's instructions.
What is the half-life of Mounjaro?
Mounjaro's elimination half-life is about 5 days, per the FDA label: that is how long it takes for the amount of tirzepatide in your body to halve. Levels peak 8 to 72 hours after a dose, and on the label schedule (a weekly injection) they reach steady state about 4 weeks after the first dose. After a last dose they fall below 5% of that steady level in about 3 weeks.
Between scheduled doses, levels swing between a peak and a trough of about 44% of that peak, which is why the chart looks like a sawtooth rather than a flat line. The label also reports that 80% of each dose is absorbed into circulation; the chart's mg figures build that in.
What if you miss a dose of Mounjaro?
The Mounjaro label instructs that a missed dose be taken as soon as possible within 4 days (96 hours), and skipped if more than 4 days have passed, with the next dose on the regular day.
That window is the half-life doing the work: with about 5 days of half-life, a late dose still lands on a meaningful base. This is the label's instruction to prescribers, not our advice; if you have missed a dose, your own label and prescriber are the authority.
Is the Mounjaro half-life the same in the UK and Australia?
Yes. The pharmacokinetics do not change with geography: the 5-day half-life, the roughly 4-week build to steady state, and the month-long taper after a last jab are properties of tirzepatide, and the UK and US Mounjaro labels both give a half-life of approximately 5 days. What differs by country is which brand carries the weight-loss indication, the pen strengths on the shelf, and the escalation schedule your prescriber follows.
If supply gaps have made your dosing irregular, the missed-dose window above is the label's rule of thumb, and the calculator shows what an occasional late jab does to your level: less than most people fear, because each dose still lands on a substantial base.
FAQ
Is Mounjaro out of your system faster at lower doses?
No. Elimination is proportional, so 2.5 mg and 15 mg decline along the same percentage curve on the same timeline. A lower dose means less tirzepatide at every point, not a faster exit.
When is Mounjaro strongest in your system?
Between 8 to 72 hours after the jab, when the amount of tirzepatide in your body peaks, per the label. From there it falls by half about every 5 days until the next dose tops it up, so the lowest point of each week is just before your next scheduled injection.
Does Mounjaro build up in your body over time?
Yes, for roughly the first month. Each weekly jab lands on top of what is left of the previous ones, so the level climbs for about 4 weeks and then settles into a steady peak-and-trough rhythm. That is also why the label has you stay at least 4 weeks on a dose before moving up: the level has not finished building until then.
Why does Mounjaro feel weaker right before the next dose?
Two things stack. By the end of the week your level really is at its trough, about 44% of the post-dose peak. But blood level is not the same as felt effect: appetite suppression has its own timetable, and receptors adjust, so the day-6 dip many people report is real without meaning the medication is gone.
Does a higher Mounjaro dose take longer to leave your system?
Not meaningfully. Mounjaro is eliminated proportionally: the amount cleared per day is a fixed fraction of what remains, so every dose falls along the same percentage curve on the same timeline. A higher dose means more tirzepatide at every point, not a longer goodbye.
Are these numbers my actual blood levels?
No. The curve is a population estimate built from the FDA label's median half-life and absorption figures: anyone who took the same doses on the same days would see the same chart. Individual metabolism runs faster or slower than the median, so treat it as the shape and rough scale of your levels, not a measurement.
Is this calculator free, and do I need to sign up?
Yes, it is free, and no sign-up or email is required. You see the full curve and the estimated clearance timeline instantly. The GlucoPal iOS app it comes from is also free to download.
Related calculators
- Mounjaro dosage chartThe label steps from 2.5 mg to 15 mg, on a calendar.
- GLP-1 half-life calculatorAll nine medications side by side: build-up, steady state, and clearance.
- Mounjaro weight loss calculatorSURMOUNT-1 averages in kilograms for the UK and Australia.
- Zepbound half-lifeThe same tirzepatide clock, US brand.
Sources
Built and maintained by GlucoPal, the free app for iPhone and Android for tracking GLP-1 weight loss medications. All pharmacokinetic figures were read directly from the current FDA label on DailyMed on 27 August 2026 and re-checked on 2 October 2026.
You take your GLP-1s. We'll take care of the rest.
