Tirzepatide Half-Life Calculator
Tirzepatide has a half-life of about five days — shorter than semaglutide's week, but still long enough for a weekly shot. This free calculator charts your estimated levels between doses: how much is left when the next one lands, how long levels keep climbing, and how long tirzepatide takes to clear.
Half-life 5 days · peaks at 36 hours
Every 7 days.
Half-life
Left at next dose
Tirzepatide (Mounjaro, Zepbound) · once weekly · levels plateau after ~25 days
Steady-state peak
8.01 mg
Steady-state trough
3.68 mg
Accumulation
1.6×
At once weekly, each dose lands before the previous one has cleared, so levels stack to about 1.6× a single dose before plateauing — roughly 25 days in. After the last dose it takes about 25 days to clear.
This is a modelled estimate of relative levels from published half-life and time-to-peak figures — not a measured blood concentration. Individual pharmacokinetics vary.
Based on a published tirzepatide half-life of ~120 hours. Models relative levels, not a measured blood concentration.
Never do this math twice.
The Pep AI app remembers your vials and doses, shows an interactive syringe you draw to, counts down the doses left in each vial, and reminds you when it's time. Free on iOS and Android.
What a 5-day half-life means in practice
Tirzepatide's roughly 120-hour half-life sits comfortably inside a 7-day dosing interval. That changes the curve in three ways:
1. One half-life
Half the dose is gone after 5 days. After two half-lives 25% remains, after three 12.5%.
2. What's left at the next dose
Dosing once a week means the next dose lands 7 days later, with about 38% of the previous one still present.
3. Accumulation and plateau
Those leftovers stack until intake matches elimination — about 1.6× a single dose, reached after roughly 25 days (five half-lives).
Worked example
Tirzepatide (Mounjaro, Zepbound) has a half-life of 5 days. Dosing once a week, the next dose arrives 7 days later with about 38% of the previous one still on board. Levels therefore stack to roughly 1.6× a single dose before plateauing, which takes about 25 days — and after a final dose it takes about the same again to clear.
How tirzepatide's curve differs from semaglutide's
Five days is meaningfully shorter than seven, and the gap shows up in the shape of the week. By the time the next weekly shot is due, a little under 40% of the previous dose is still present — compared with a full 50% for semaglutide. Less carries over, so levels stack less: tirzepatide plateaus at roughly 1.6× a single dose, where semaglutide reaches about 2×.
The practical effect is a slightly more pronounced peak-to-trough swing across the week, and a faster approach to steady state — about 25 days rather than 35. Some people notice the back half of the week feeling different from the first couple of days after a shot; a shorter half-life is part of why.
It also means clearance is quicker. Roughly 25 days after a final dose, tirzepatide is about 97% eliminated, against five weeks for semaglutide.
Because titration keeps changing the dose, the curve is a moving target — Pep AI models it from your real logged shots at every step. The tirzepatide tracker keeps shot day, titration, food, and weight in the same place.
Frequently asked questions
This calculator is provided for informational and educational purposes only and is not medical advice. Always confirm dosing with a qualified healthcare professional and double-check your own measurements before administering anything.