Tirzepatide and semaglutide level calculator
Short answer: Tirzepatide (Mounjaro, Zepbound) has a half-life of about 5 days and semaglutide (Wegovy, Ozempic) about 7 days, according to their labels. With weekly doses, both build up over the first month or so, then level off. The chart below gives an illustrative estimate for your schedule, including how long it takes to clear after the last dose.
What the chart shows for weekly GLP-1 doses
- Tirzepatide: with a 5-day half-life and weekly doses, roughly 38% of the level is left when the next dose is due. Levels settle after about 3 to 4 weeks at the same dose.
- Semaglutide: with a 7-day half-life, about half is left a week later, so the curve is flatter and takes about 4 to 5 weeks to settle at each dose.
That build-up is one reason the first weeks at a new dose can feel different from later weeks, and why many people notice appetite returning in the last day or two before their next jab. Titration plans step up gradually for the same reason. Your prescriber sets the plan.
Try these
- Switch between tirzepatide and semaglutide to compare how flat each curve is.
- Set the number of doses to 1 and look at how long a single dose takes to clear.
- Enter your amounts to see estimates in mg, noting that the chart does not model dose steps.
See your real curve, from your real doses
This page assumes a perfectly regular schedule. Real life has late doses, skipped weeks and dose changes. PepLevel builds the same kind of illustrative estimate from the doses you actually logged, with a marker for right now, for any compound with a half-life. Most people use it to make sense of hunger coming back, side effects on certain days, or the build-up after a dose change. The basic curve is free, and Pro can overlay your weight and side effects on it. It is always labelled as an estimate, never a blood test.
Common questions
How long does Mounjaro stay in your system?
Tirzepatide's half-life is about 5 days, so it takes around 25 days (5 half-lives) after the last dose for most of it to clear, according to the label figure.
Why does my Mounjaro seem to wear off before my next dose?
With a 5-day half-life, the level is lowest just before the next weekly dose, at roughly 38% of the previous peak in this model. Some people notice appetite returning then. Mention it to your prescriber.
How long does semaglutide take to build up?
With a half-life of about a week, semaglutide takes around 4 to 5 weeks at a steady weekly dose to reach a stable level.
PepLevel does this from your own doses
Saved vials, planned doses in mL, and a level curve built from what you actually logged. Coming soon to the App Store.
Get PepLevelMedical disclaimer: this tool does arithmetic and illustrative estimates only. It is not medical advice, does not recommend any dose and is not a substitute for your prescriber, pharmacist or the product information. PepLevel is a logging and reminder tool only.