Mounjaro Half-Life Calculator
Mounjaro is tirzepatide with a half-life of about 5 days, so each weekly jab still has roughly half its level on board when the next one is due. See your estimated level at any day, building up or after stopping.
Free · instant chart · no sign-up or email · built on the Mounjaro FDA label
Mounjaro half-life chart: estimated mg in your body, day by day
Estimated tirzepatide in your body, day 42 after your first dose
steady rhythm: ~11.4 mg peak, ~5.1 mg trough
Free · No account required · iPhone
Quick answer: Mounjaro's elimination half-life is about 5 days. From steady weekly use, a last injection falls below 5% of your usual level in about 3 weeks; from a first dose, levels build to steady state in about 4 weeks. In the UK and Australia Mounjaro is the tirzepatide brand prescribed for weight loss; in the US the same molecule for weight loss is sold as Zepbound, and the clock is identical.
Educational estimate only, not medical advice. Individual pharmacokinetics vary, and blood level is not the same thing as appetite effect. Never change your dose or schedule without your prescriber.
The Mounjaro half-life arithmetic
Mounjaro is tirzepatide, with an elimination half-life of about 5 days and peak levels 24 hours (range 8 to 72) after a dose, per the FDA label. On the label schedule (a weekly injection), levels reach steady state about 4 weeks after the first dose, and 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 calculator's chart looks like a sawtooth rather than a flat line. The label also reports that 80%of each dose is absorbed into circulation; the calculator's mg figures build that in.
What the Mounjaro label says about a missed dose
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 daysof 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.
The Mounjaro clock for UK and Australian readers
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 UK, Australian, and US labels report the same figures. 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
How long does Mounjaro stay in your system?
About a month: tirzepatide's 5-day half-life means a last Mounjaro injection falls to half in 5 days and below 5% of the steady level in about 3 weeks. The taper is gradual, so effects fade over weeks rather than stopping on a date.
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?
About 24 hours (range 8 to 72) 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.
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Sources
This free calculator is built and maintained by GlucoPal, the free iPhone app for tracking GLP-1 weight loss medications. All pharmacokinetic figures were read directly from the current FDA label on DailyMed on 27 August 2026.
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