Comparing GLP-1 medicines
Mounjaro vs Zepbound: What Differs?
Mounjaro and Zepbound both contain tirzepatide. See how the US labels differ on use, dose steps and side effects, and why the EU and UK have no Zepbound.
Guides
Semaglutide vs Tirzepatide: What Trials Show
Semaglutide and tirzepatide differ first in mechanism. The Ozempic label lists semaglutide as a GLP-1 receptor agonist, and the Mounjaro label lists tirzepatide as a GIP and GLP-1 receptor agonist. In SURMOUNT-5, the head-to-head trial, average weight reduction at 72 weeks was higher with tirzepatide than with semaglutide. Which medicine suits a person is a decision for that person and their prescriber, not for a table. Each figure below comes with its population, dose and duration.
In short
- The Ozempic and Mounjaro labels describe semaglutide as a GLP-1 receptor agonist and tirzepatide as a GIP and GLP-1 receptor agonist.
- In SURMOUNT-5, average weight reduction at 72 weeks was 21.6% with tirzepatide and 15.4% with semaglutide, as reported by a secondary analysis citing the trial.
- The Wegovy label reports nausea in 44% of adults on 2.4 mg, and the Zepbound label 25% to 29% on 5 to 15 mg, from separate placebo-controlled trials.
Semaglutide vs tirzepatide: what is the difference?
The US prescribing information for Ozempic, Wegovy, Mounjaro and Zepbound shows that semaglutide and tirzepatide differ in mechanism, approved use and label dose steps. The table sets them side by side. All lines are US FDA label or trial data.
| Semaglutide | Tirzepatide | |
|---|---|---|
| Mechanism (label section 12.1) | GLP-1 receptor agonist | GIP and GLP-1 receptor agonist |
| US diabetes brand and use | Ozempic: glycemic control in type 2 diabetes, plus cardiovascular and kidney risk reduction | Mounjaro: glycemic control in type 2 diabetes (ages 10 and over), plus cardiovascular risk reduction |
| US weight brand and use | Wegovy: chronic weight management in adults and adolescents 12 and over with obesity, or overweight with a comorbidity | Zepbound: chronic weight reduction and maintenance in adults with obesity, or overweight with a comorbidity; moderate to severe sleep apnea with obesity |
| Label dose steps for weight | Wegovy: 0.25, 0.5, 1 and 1.7 mg, 4 weeks each, then 2.4 mg maintenance | Zepbound: 2.5 mg for 4 weeks, up 2.5 mg every 4 weeks, maintenance 5, 10 or 15 mg |
| SURMOUNT-5 average weight reduction, 72 weeks, adults with obesity and no diabetes | 15.4% (1.7 or 2.4 mg weekly) | 21.6% (10 or 15 mg weekly) |
| Nausea, weight-management label, vs placebo | 44% on 2.4 mg (placebo 16%) | 25% to 29% on 5 to 15 mg (placebo 8%) |
| Vomiting, same tables | 24% (placebo 6%) | 8% to 13% (placebo 2%) |
| Diarrhea, same tables | 30% (placebo 16%) | 19% to 23% (placebo 8%) |
Only the SURMOUNT-5 row is head to head. The side-effect rows come from separate trials and cannot be compared directly. The label schedules are the manufacturers' own, and the prescriber decides the dose.
What did the SURMOUNT-5 trial compare and find?
SURMOUNT-5 compared once-weekly tirzepatide with once-weekly semaglutide in 751 adults with obesity and no diabetes, according to a secondary analysis that cites the trial design. It was a phase 3b, open-label trial. Each person took the maximum tolerated dose for 72 weeks: tirzepatide 10 or 15 mg, or semaglutide 1.7 or 2.4 mg.
Average body weight fell by 21.6% with tirzepatide and 15.4% with semaglutide, using the efficacy estimand, as reported by that secondary analysis. The gap is 21.6 minus 15.4, or 6.2 percentage points.
These are group averages, not a prediction for any one person. They do not show results at lower doses, beyond 72 weeks, or in people with type 2 diabetes. The primary record is Aronne et al., N Engl J Med 2025;393(1):26-36, under PubMed ID 40353578.
What do the labels say about side effects?
The four US prescribing information documents list nausea, vomiting and diarrhea in their adverse-reaction tables, each from that drug's own placebo-controlled trials. The weight-management rates for Wegovy and Zepbound are in the table above. The type 2 diabetes rates for Ozempic and Mounjaro (percent of participants, section 6.1, Table 1 of each label) are below.
| Reaction | Ozempic 0.5 mg | Ozempic 1 mg | Ozempic placebo | Mounjaro 5 mg | Mounjaro 10 mg | Mounjaro 15 mg | Mounjaro placebo |
|---|---|---|---|---|---|---|---|
| Nausea | 15.8% | 20.3% | 6.1% | 12% | 15% | 18% | 4% |
| Vomiting | 5% | 9.2% | 2.3% | 5% | 5% | 9% | 2% |
| Diarrhea | 8.5% | 8.8% | 1.9% | 12% | 13% | 17% | 9% |
The type 2 diabetes tables come from different trials than the weight-management tables, so the two sets should not be mixed. Every listed rate is above its own placebo rate. Each table has its own population, doses and duration, so none of this is a head-to-head measure.
The labels' Warnings and Precautions sections name signs that call for medical care: severe or persistent stomach pain, with or without vomiting, which can point to pancreatitis; symptoms of gallbladder problems; signs of dehydration, since vomiting or diarrhea can lead to kidney injury; and signs of a severe allergic reaction, such as swelling of the face or trouble breathing. Each label has the full wording.
How often do people stop treatment because of side effects?
The Wegovy and Zepbound labels report gastrointestinal-related permanent discontinuation in their weight-management trials. On the Wegovy label, it was 4.3% on 2.4 mg against 0.7% on placebo.
On the Zepbound label, pooled Studies 1 and 2 show 1.9% on 5 mg, 3.3% on 10 mg and 4.3% on 15 mg, against 0.5% on placebo.
These come from separate trials with different populations and durations. They report the share who stopped for gastrointestinal reasons. They do not say why any one person stopped. Any decision about dose or stopping belongs to the prescriber.
How long does each drug stay active in the body?
The Ozempic label gives semaglutide an elimination half-life of approximately 1 week, and the Mounjaro and Zepbound labels give tirzepatide approximately 5 days, or 5 to 6 days in people with overweight or obesity (section 12.3). The same section lists absolute bioavailability of 89% for semaglutide and 80% for tirzepatide.
A half-life is the time for the amount in the body to fall by half. It is a population figure from the label, not a measurement of one person.
For a day-by-day view, a worked week-by-week decay table for Ozempic's half-life beside Mounjaro's applies these numbers. The calculator that estimates how much semaglutide or tirzepatide your own doses leave in the body uses the same label figures, and the free GLP-1 tools index lists the rest.
What brands contain semaglutide and tirzepatide?
Among the products whose labels are cited here, semaglutide is sold in the US as Ozempic and Wegovy, and tirzepatide as Mounjaro and Zepbound. Ozempic and Mounjaro are labelled for type 2 diabetes, and Wegovy and Zepbound for weight management, as the table above shows.
The Ozempic and Mounjaro pages carry the diabetes data. The figures in this article describe those four brand labels, not other products or compounded versions.
Other countries have their own approvals. The EU, UK and other markets publish their own product information, which can show different doses or indications from the US labels used here.
What does the shared boxed warning cover?
The Ozempic, Mounjaro, Wegovy and Zepbound labels all carry the same boxed warning about a risk of thyroid C-cell tumors seen in rodent studies. The labels state that the relevance to humans is unknown.
All four are contraindicated in people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2 (MEN 2), so that history matters to the prescriber.
The labels say to seek medical care for a lump or swelling in the neck, trouble swallowing or hoarseness. The warning is the same for both molecules, so it does not separate them. The full wording is on each label, for example the Mounjaro prescribing information.
Can an app track either medicine?
Dose & Lose is a tracking app that supports both semaglutide and tirzepatide products, including Ozempic, Wegovy, Mounjaro and Zepbound. It logs each dose with its injection site and notes, and lets you rate symptoms such as nausea from 0 to 10 day by day.
It also draws an estimate of the medication level from the doses you logged, using a fixed model per medication. That is an estimate, not a lab value. The app does not prescribe, supply or give dosing advice. The app page describes how it logs doses and side effects.
Frequently asked questions
Is tirzepatide stronger than semaglutide?
The sources do not support calling either medicine stronger. In SURMOUNT-5, tirzepatide's average weight reduction was higher than semaglutide's in adults with obesity and no diabetes over 72 weeks, but that describes one population, doses and an open-label design. Choosing between them stays with the reader and their prescriber.
Can I switch from semaglutide to tirzepatide?
The labels quoted here give no switching schedule, so the new dose is a prescriber's decision. Each label gives its own starting dose and steps: Wegovy starts at 0.25 mg and Zepbound at 2.5 mg, for people starting treatment. Those are label schedules for starting, not instructions for changing medicine. Ask your prescriber before any change.
Does the SURMOUNT-5 trial apply to people with type 2 diabetes too?
SURMOUNT-5 enrolled adults with obesity and no diabetes, so its averages do not describe people with type 2 diabetes. The Ozempic and Mounjaro labels report their own type 2 diabetes trial tables, which are separate from the weight-management tables. A prescriber can say which evidence fits a person's situation.
What is retatrutide and how does it relate to these two?
Retatrutide is a separate molecule from semaglutide and tirzepatide, and no label or trial figures for it are cited here. A fair comparison would need its own label or trial data. Ask a prescriber, and read the regulator's current record before relying on claims found elsewhere.
Sources
- Ozempic prescribing information: semaglutide mechanism, half-life, boxed warning, type 2 diabetes reactions.
- Mounjaro prescribing information: tirzepatide mechanism, half-life, boxed warning, type 2 diabetes reactions.
- Wegovy prescribing information: weight dosing, indications, reactions, discontinuation.
- Zepbound prescribing information: weight dosing, indications, reactions, discontinuation.
- SURMOUNT-5, Aronne et al., NEJM 2025, PubMed ID 40353578: the head-to-head trial record.
- Truveta cohort study citing SURMOUNT-5 (PMC12924827): trial design and weight figures.
Published by Petros IT Solutions SRL, byline Dose & Lose Editorial Team. Corrections: office@doseandlose.com.