Tirzepatide Weight Loss Calculator
Quick answer: In SURMOUNT-1, adults on 15 mg weekly tirzepatide lost an average of 20.9% of body weight over 72 weeks — about 46 lb for a 220 lb person — the strongest result of any approved weight-loss medication. In the head-to-head SURMOUNT-5 trial it beat semaglutide directly (20.2% vs 13.7%). Enter your weight below for your projection.
Projection uses SURMOUNT-1 trial averages — population averages with full titration and lifestyle support. Individual results vary widely; roughly 1 in 7 participants were non-responders.
Tirzepatide dose schedule
| Phase | Dose | Notes |
|---|---|---|
| Weeks 1–4 | 2.5 mg weekly | Starter dose — tolerance building |
| Weeks 5–8 | 5 mg weekly | First maintenance-eligible dose |
| Weeks 9–12 | 7.5 mg weekly | Escalation continues if tolerated |
| Weeks 13–16 | 10 mg weekly | Mid maintenance dose |
| Weeks 17–20 | 12.5 mg weekly | Penultimate step |
| Week 21+ | 15 mg weekly | Top dose used in SURMOUNT-1 |
The trial record: why tirzepatide leads the class
SURMOUNT-1 (2022, NEJM) enrolled 2,539 adults without diabetes: the 15 mg arm averaged 20.9% body-weight loss at 72 weeks, with 36% of participants losing a quarter of their body weight or more — numbers previously seen only with bariatric surgery. The 5 mg and 10 mg arms still delivered 15-19.5%.
The comparison everyone wanted came in SURMOUNT-5 (2025): tirzepatide head-to-head against semaglutide 2.4 mg produced 20.2% versus 13.7% average loss at 72 weeks — a decisive win that reshaped prescribing. Tirzepatide has since added an obstructive sleep apnea approval (SURMOUNT-OSA) to the label.
Why two receptors beat one
Tirzepatide pairs GLP-1 agonism with GIP — a second incretin receptor that appears to amplify fat oxidation and insulin sensitivity while, counterintuitively, easing the GI side-effect load per unit of effect. The practical translation: more loss at tolerability comparable to semaglutide, which is exactly what the head-to-head showed.
Month-by-month expectations
The shape mirrors other incretins but steeper: modest movement in the 2.5-5 mg titration months (1-2 months in), then a fast phase from months 3 through 9 as doses climb toward 10-15 mg, followed by a slow taper toward plateau around month 15-16. In SURMOUNT-1 the curve was still gently declining at week 72 in the top-dose arm — the ceiling appears higher than semaglutide's.
Dose matters here more than with semaglutide: the spread between 5 mg (~15%) and 15 mg (~21%) arms is wide, so how far you titrate is a genuine lever, balanced against tolerability.
Side effects and the practical playbook
The profile is the incretin standard: nausea (~25-30%), diarrhea, constipation, mostly during escalation and mostly transient. The same rare-but-serious list applies — pancreatitis, gallbladder events, the rodent thyroid C-cell warning (medullary thyroid carcinoma/MEN2 history is a contraindication).
Management mirrors semaglutide: slow the ramp when a step bites, protein-first smaller meals, hydration. With larger vials in the compounded/gray market (up to 30 mg), the dosing-math stakes are higher — a concentration mistake on a 30 mg vial is a multi-week overdose, which is why the reconstitution calculator exists.
Muscle, maintenance and stopping
Lean-mass loss tracks with speed of loss, and tirzepatide is the fastest — making protein targets (1.8+ g/kg) and twice-weekly resistance training effectively part of the prescription. On stopping: SURMOUNT-4 randomized people to continue or switch to placebo after 36 weeks; the placebo group regained about 14% of body weight over the following year while continuers kept losing. Same conclusion as semaglutide, louder: this is chronic therapy, not a course.
FAQ
How much weight can I lose on tirzepatide in 3 months?+
Trial-average pace suggests roughly 7-9% of body weight by month 3 — for a 220 lb person, 15-20 lb — with the caveat that months 1-2 are low-dose titration and individual spread is wide.
Is tirzepatide better than semaglutide for weight loss?+
On averages, yes — SURMOUNT-5 showed 20.2% vs 13.7% head-to-head. Individually it's less absolute: some people respond better to one than the other, and tolerability or availability often decides in practice.
Mounjaro vs Zepbound — what's the difference?+
Identical molecule and doses; Mounjaro is the type-2-diabetes label, Zepbound the weight-management (and sleep apnea) label. The SURMOUNT weight numbers apply to both at equal doses.
Do I need to reach 15 mg for results?+
No — 5 mg averaged ~15% in SURMOUNT-1, already matching semaglutide's best. Many prescribers hold patients at the highest well-tolerated dose rather than forcing the climb to 15 mg.
Educational content based on published clinical trial data. Projections are population averages, not personal predictions, and nothing here is medical advice — treatment decisions belong with a licensed prescriber.