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Mounjaro half-life calculator
How long does Mounjaro (tirzepatide) stay in your system? Its half-life is ≈ 5 days (about 120 hours) — enter your last dose to estimate what's left today, and see it clear half-life by half-life.
GLPMate models your actual tirzepatide level day by day from your real dose history — free.
Defaults to today. This estimates what's left from that single dose.
Right after a dose, 100% is on board. Pick your last dose date above to estimate today's level.
How Mounjaro clears, half-life by half-life
Days are counted from your last dose (5 days per half-life). After ~5 half-lives (25 days) only about 3% remains — effectively cleared.
How long does Mounjaro stay in your system?
The short answer: about 25 days after your last dose. Mounjaro's elimination half-life is ≈ 5 days (about 120 hours), and it takes roughly five half-lives for ~97% of a dose to leave your body. The table below shows the standard decay.
| Time since last dose | Approx. remaining |
|---|---|
| 5 days (1 half-life) | 50% |
| 10 days (2 half-lives) | 25% |
| 15 days (3 half-lives) | 12.5% |
| 20 days (4 half-lives) | 6.3% |
| 25 days (5 half-lives) | 3.1% |
The formula
This is first-order elimination — the same math clinicians use:
remaining = 0.5 ^ (days since dose ÷ 5)
It's a single-dose estimate. If you've been dosing for a while, you start clearing from a higher accumulated level, so in practice it can take slightly longer than the single-dose figure — but ~5 half-lives from your last dose is the widely used rule of thumb.
Why the half-life cuts both ways
Mounjaro (tirzepatide)'s long half-life is exactly why your level builds up over the first month and fades slowly when you stop. Understanding your own level — not just guessing — is what GLPMate's free medication-level plotter and in-app curve are for.
Source: FDA Prescribing Information clinical-pharmacology data for Mounjaro. Educational estimate — not medical advice.
Mounjaro® is a trademark of Eli Lilly. GLPMate is an independent tracking app and is not affiliated with, endorsed by, or connected to Eli Lilly.
This tool is for general education only — not medical advice, not a diagnosis, and not a substitute for your prescriber or pharmacist. Half-life figures are population averages; your own clearance depends on your metabolism, kidney function and dose history. Never start, stop or change Mounjaro based on a web calculator.
Sources
- FDA Prescribing Information (label) for each product — clinical-pharmacology sections — elimination half-life per active ingredient
- First-order elimination model — remaining fraction = 0.5 ^ (time ÷ half-life)
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Mounjaro half-life questions
How long does Mounjaro stay in your system?
Mounjaro's elimination half-life is ≈ 5 days (about 120 hours). It takes roughly 5 half-lives to clear about 97% of a dose, so that's around 25 days after your last dose. A tiny amount lingers longer, but it's usually not clinically meaningful. This calculator estimates what's left on any given day from your last dose.
What is a drug half-life, exactly?
A half-life is the time it takes for your body to clear half of the drug. After one half-life 50% remains, after two 25%, then 12.5%, and so on. Mounjaro's 5 days half-life is why it both builds up gradually when you start and clears slowly when you stop.
Why does Mounjaro take weeks to build up if the half-life is only 5 days?
The same half-life that slows clearance also slows accumulation. With weekly dosing, each dose stacks on what's left of the previous ones until you reach a steady state — usually after about 4–5 weeks at a constant dose. GLPMate's medication-level curve shows this build-up on your real schedule.
How does this calculator estimate what is left?
It uses first-order elimination: fraction remaining = 0.5 ^ (days since dose ÷ half-life in days), with the half-life taken from Mounjaro's clinical-pharmacology data. It's a single-dose educational estimate — real levels also depend on accumulation from earlier doses, your metabolism and kidney function.
Can I make Mounjaro leave my body faster?
Not reliably. Clearance is set by the drug's chemistry and your own physiology — extra water, exercise or supplements don't meaningfully speed it up. If you need it out of your system for a procedure or pregnancy planning, that's a conversation for your prescriber, who will plan around the half-life.
Is this calculator affiliated with Eli Lilly?
No. GLPMate is an independent tracking app. Mounjaro® is a trademark of Eli Lilly; we're not affiliated with or endorsed by them. We just help you track your prescribed treatment.
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