Mounjaro vs Ozempic: what the head-to-head trial shows

Mounjaro and Ozempic at a glance

Mounjaro and Ozempic are brand names. The medicine inside each one is what the trials tested, so this page uses both names. The tirzepatide page and the semaglutide page have the full details.

Uses and strengths are from the DailyMed labels the Atlas read (versions read: Mounjaro 8/2026, Ozempic 5/2026). The two companies use different strengths, so the numbers are not interchangeable and the Atlas gives no conversion between them. See the brand and generic names page for how the products relate.

What did the head-to-head trial find?

SURPASS-2 is the trial that put the two medicines in the same study. It enrolled 1,879 adults with type 2 diabetes. Each person was assigned to tirzepatide 5 mg, 10 mg or 15 mg, or to semaglutide 1 mg, and followed for 40 weeks. It was open label, so participants and staff knew which medicine was in use.

Source: SURPASS-2, published in the New England Journal of Medicine in 2021. The Atlas read the published abstract. Participants had a baseline HbA1c of 8.28% and an average weight of 93.7 kg. Group averages do not predict one person's result.

Why the SURPASS-2 result needs care

Tirzepatide came out ahead on both blood sugar and weight in this trial, and the gaps grew with the tirzepatide dose. It is still a single trial, and a few details limit how far it reaches.

• Eli Lilly, which makes tirzepatide, funded it, and Lilly employees are among the authors. Funding does not make a result wrong. It is a reason to want other trials to agree.
• It was open label, which can affect how people report side effects and how they behave in a trial.
• The semaglutide group took 1 mg. Ozempic's label goes up to 2 mg. In SUSTAIN FORTE, a separate Novo Nordisk trial of 961 adults with type 2 diabetes, semaglutide 2 mg lowered HbA1c by 2.2 points and semaglutide 1 mg by 1.9 points over 40 weeks, and body weight fell by 6.9 kg and 6.0 kg. Those figures leave out people who stopped treatment or needed rescue medication. Counting everyone randomized, HbA1c fell by 2.1 and 1.9 points and weight by 6.4 and 5.6 kg. It is a separate trial, so its numbers should not be set beside the SURPASS-2 table. The Atlas found no published head-to-head trial of tirzepatide against semaglutide 2 mg.
• It lasted 40 weeks and enrolled adults with type 2 diabetes. It does not show what happens over several years, in people without diabetes or in other groups.
• It measured blood sugar first. Weight was a secondary result. The weight gaps in the table are differences between groups, not the total weight each group lost.

What about weight loss?

This is the question behind many searches for Mounjaro and Ozempic, and it is where the product names get tangled. Neither label lists weight loss as a use. Weight management is the label of the counterparts: Zepbound (tirzepatide) and Wegovy (semaglutide). The weight-loss trials were run on those products. A prescriber who uses a diabetes-labeled product to treat weight is prescribing off-label. The Atlas does not advise on that.

The trials built to test weight loss in people with type 2 diabetes and obesity centered on the higher weight-management strengths. STEP 2 also had a semaglutide 1.0 mg arm, but the abstract the Atlas read gives no weight result for it. In SURMOUNT-2, 938 adults lost an average of 12.8% on tirzepatide 10 mg and 14.7% on 15 mg over 72 weeks, compared with 3.2% on placebo. In STEP 2, 1,210 adults lost an average of 9.6% on semaglutide 2.4 mg over 68 weeks, compared with 3.4% on placebo. Those are separate trials, run by different companies, so the two sets of numbers should not be lined up as if they came from one experiment.

For the head-to-head comparison in adults with obesity and without type 2 diabetes, see Zepbound vs Wegovy. Other registered trials that put two medicines against each other are sorted on the combination and head-to-head trials page.

How do the side effects compare?

The two labels describe the same family of effects. For Mounjaro, the common ones listed are nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion and abdominal pain. For Ozempic, they are nausea, vomiting, diarrhea, abdominal pain and constipation. Both labels carry a boxed warning about thyroid C-cell tumors seen in rodents, and neither product is for people with a personal or family history of medullary thyroid carcinoma or MEN 2.

In SURPASS-2, digestive effects were the most common side effects in every group and were mostly mild to moderate. The rates in the table above are the cleanest comparison available, because both medicines were in one trial. Rates quoted from each label come from different trials and different people, so they should not be set side by side. The week-by-week side effects page shows when digestive effects tend to appear as doses rise.

Does coverage separate them?

It can. Both products are labeled for type 2 diabetes, and plans, Medicare programs and maker offers treat the two differently. Prices and offers change often, so this page lists none. The paying for GLP-1 medicines page covers the main ways people pay, and the Medicare page covers what the program pages describe.

Which one is right for me?

A trial average cannot answer that. A prescriber looks at things the trials cannot: your health conditions, kidney function, other medicines, how you handle side effects, what your plan covers and what is in stock. The first visit page and the questions to ask your prescriber help you prepare.

What about compounded versions?

Compounded versions are made by pharmacies, are not FDA-approved and are not reviewed by the FDA for safety, effectiveness or quality before they are sold. The numbers on this page describe the approved products. See compounded versus brand-name medicines.

Quick answers

Is Mounjaro better than Ozempic?

In SURPASS-2, adults with type 2 diabetes had larger average drops in HbA1c and body weight on tirzepatide than on semaglutide 1 mg over 40 weeks. The trial was open label and funded by Eli Lilly, and the semaglutide group did not take the 2 mg strength that Ozempic's label allows. Which is better for one person depends on their health, side effects, cost and coverage.

Which causes more weight loss, Mounjaro or Ozempic?

In SURPASS-2, people on tirzepatide lost 1.9 kg (5 mg), 3.6 kg (10 mg) and 5.5 kg (15 mg) more than people on semaglutide 1 mg. Weight was a secondary result, and neither label lists weight loss as a use.

Is Mounjaro the same as Zepbound?

Both contain tirzepatide. They are separate products with separate labels. Mounjaro's label lists type 2 diabetes, and Zepbound's lists weight management and obstructive sleep apnea. The Atlas's brand names page lays out how the products relate.

Is Ozempic approved for weight loss?

No. The Ozempic label lists type 2 diabetes uses. Wegovy, which also contains semaglutide, is the product labeled for weight reduction.

Do Mounjaro and Ozempic work the same way?

Not exactly. Ozempic's semaglutide switches on the GLP-1 receptor. Mounjaro's tirzepatide switches on both the GLP-1 and GIP receptors. The Mounjaro and Ozempic injections are both weekly.

Are the side effects different?

Both labels list digestive effects as the common ones. In SURPASS-2, nausea was reported by 17% to 22% of people on tirzepatide and 18% on semaglutide, diarrhea by 13% to 16% and 12%, and vomiting by 6% to 10% and 8%. Both carry a boxed warning about thyroid C-cell tumors seen in rodents.

Can you switch from Ozempic to Mounjaro?

SURPASS-2 compared people who started on one medicine or the other, not people who switched. The switching page covers what the labels say and the small studies that exist.

What is the Mounjaro dose range?

The label the Atlas read starts at 2.5 mg weekly, raises the dose in 2.5 mg steps after at least 4 weeks, and lists 15 mg as the highest weekly dose in adults. A prescriber sets the plan, and the Atlas does not advise on doses.

Questions to ask

• Given my health history and the other medicines I take, how do Mounjaro and Ozempic differ for me?
• Which uses on each label match my diagnosis, and how does my plan treat that?
• What would each cost me with my coverage, including after the first month?
• Which side effects should I expect with each one, and when should I call?
• If the first medicine does not suit me, what is the plan?

What is still unknown

• The Atlas found one head-to-head trial in adults with type 2 diabetes. It was open label and funded by the maker of tirzepatide, and the Atlas found no independent repeat of it.
• The Atlas found no published head-to-head trial of tirzepatide against semaglutide 2 mg, the highest strength on Ozempic's injection label. A small registered trial in Saudi Arabia (NCT07820111, 159 people) lists semaglutide 2 mg among its arms and has no posted results.
• How the two medicines compare beyond 40 weeks, or on heart and kidney outcomes, is not shown by the trials on this page.
• The Atlas read the published abstracts of these trials, not the full papers, so it does not list every side-effect rate.
• Weight-loss results in the trials come from the weight-management products and strengths. The Atlas found no dedicated head-to-head weight-loss trial of the two medicines in people with type 2 diabetes. In SURPASS-2, weight was a secondary result.