The Short Answer
Mounjaro (tirzepatide) has produced more weight loss than Ozempic (semaglutide) whenever researchers have compared the two molecules directly. The clearest evidence comes from SURMOUNT-5, a trial that tested the same active ingredients under their weight-management brand names, Zepbound and Wegovy, in 751 adults with obesity and without diabetes. Tirzepatide won on average weight loss. It also won on waist circumference.
That said, averages are not you. Some people respond strongly to semaglutide, some tolerate one drug better than the other, and some should not take either. So the short answer is tirzepatide by the numbers, with your prescriber holding the tiebreaker.
What the Head-to-Head Trials Show
SURMOUNT-5, published in the New England Journal of Medicine in 2025, is the most direct weight-loss comparison of these two molecules to date. It enrolled 751 adults with obesity, or overweight plus at least one weight-related condition, and no diabetes. Participants received the maximum tolerated dose of either tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) once weekly for 72 weeks. Tirzepatide cut body weight by an average of 20.2 percent. Semaglutide managed 13.7 percent. Waist circumference dropped 18.4 cm with tirzepatide versus 13.0 cm with semaglutide.
Two honest footnotes belong next to those numbers. The trial was open label, meaning participants and clinicians knew which drug was being given, and it was funded by Eli Lilly, the company that makes tirzepatide. Neither fact erases a 6.5 percentage point gap, but you should know who paid for the scoreboard.
An earlier trial, SURPASS-2, published in the New England Journal of Medicine in 2021, compared the molecules in 1,879 adults with type 2 diabetes over 40 weeks. Patients on tirzepatide 15 mg lost roughly twice as much weight as those on semaglutide. The catch: semaglutide was capped at 1 mg in that study, while Ozempic's label now runs to 2 mg. Useful data, but not a full-strength fight.
How Ozempic and Mounjaro Differ
Ozempic and Mounjaro are different molecules from different companies with different mechanisms, even though both are once-weekly injections approved for type 2 diabetes. Semaglutide, the drug in Ozempic, activates the GLP-1 receptor. Tirzepatide, the drug in Mounjaro, activates both the GLP-1 and GIP receptors, and the FDA noted it was the first dual-target drug of its kind when it approved Mounjaro in May 2022. That second receptor is the leading explanation for the larger weight effect, though researchers are still working out exactly why.
One practical note: do not compare the milligram numbers across the two drugs. They are different molecules, so 15 mg of tirzepatide and 2 mg of semaglutide are simply not on the same scale. For a deeper look at the two molecules across all their brand names, see our semaglutide vs tirzepatide comparison.
| Ozempic | Mounjaro | |
|---|---|---|
| Active ingredient | Semaglutide | Tirzepatide |
| Manufacturer | Novo Nordisk | Eli Lilly |
| Receptor target | GLP-1 | GLP-1 + GIP |
| FDA-approved for | Type 2 diabetes (December 2017) | Type 2 diabetes (May 2022) |
| Weekly dose range | Titrated up to a 2 mg maximum | Titrated from 2.5 mg up to a 15 mg maximum |
| Weight-management sibling | Wegovy (same molecule, approved for weight management) | Zepbound (same molecule, approved for weight management) |
| Common GI side effects | Nausea, vomiting, diarrhea, constipation | Nausea, diarrhea, constipation, vomiting |
Approval dates and dose ranges are drawn from FDA announcements and each medication's US prescribing information. See our GLP-1 side effects guide for the full side effect picture.
The Approval Caveat Nobody Should Skip
Neither Ozempic nor Mounjaro is FDA-approved for weight loss. The FDA approved Ozempic in December 2017 and Mounjaro in May 2022, both for blood sugar control in adults with type 2 diabetes. The weight-management approvals belong to their sibling brands: Wegovy carries semaglutide's, Zepbound carries tirzepatide's. Same molecules, different labels, different approved uses.
Why does a label matter if the molecule is identical? Insurance, mostly. Clinicians can and do prescribe Ozempic or Mounjaro off label for weight management, which is legal, but insurers generally will not pay for a diabetes drug prescribed to a patient without diabetes. That can leave you with the full list price, and these are not cheap drugs. Our GLP-1 cost guide breaks down what that means in dollars. If weight loss is your goal, ask your prescriber whether one of the weight-management versions is the more sensible route.
Which One Should You Ask About?
The better drug between Ozempic and Mounjaro, for you specifically, depends on your diabetes status, your insurance, and how your body handles each molecule, and that is a decision to make with your prescriber rather than a comparison chart. The trial averages favor tirzepatide. Your own response might not follow the average, and tolerability often decides the question in practice.
A few things worth raising in that conversation. First, whether you have type 2 diabetes, since that determines which labels even apply to you. Second, side effects: both drugs commonly cause nausea, vomiting, diarrhea, and constipation, and the prescribing information for tirzepatide products lists constipation particularly often. Third, cost and coverage, which vary more between insurance plans than between the two drugs. You can read more about each medication in our Ozempic guide and Mounjaro guide. And if you do start one of these medications, our guide to your first month on a GLP-1 covers what the opening four weeks actually look like.
Frequently Asked Questions
In head-to-head trials of their active ingredients, tirzepatide (the drug in Mounjaro) produced more weight loss than semaglutide (the drug in Ozempic). The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, reported 20.2 percent average weight reduction with tirzepatide versus 13.7 percent with semaglutide over 72 weeks. Individual responses vary widely, and neither drug is FDA-approved for weight loss. Talk with your prescriber about which medication, if any, fits your situation.
Ozempic and Mounjaro are FDA-approved for type 2 diabetes, not for weight loss. Some clinicians prescribe them off label for weight management, which is legal but usually means insurance will not cover the cost. The same active ingredients are sold as Wegovy (semaglutide) and Zepbound (tirzepatide), which are FDA-approved for chronic weight management. A licensed clinician can determine which option, if any, is appropriate for you.
Ozempic and Mounjaro share a similar gastrointestinal side effect profile. Nausea, vomiting, diarrhea, and constipation are the most commonly reported side effects in the prescribing information for both medications, with constipation reported particularly with tirzepatide products. Each drug also carries its own specific warnings. Review the official prescribing information for the medication you take and report any concerning side effect to your prescriber.
Weight change with either medication is gradual. Both drugs start at a low dose and increase stepwise over several months, and the major comparison trials measured their results at 40 to 72 weeks rather than after a few injections. SURMOUNT-5, for example, ran for 72 weeks, roughly a year and a half. Expect a process measured in months, guided by your prescriber, not a quick result.
Talk It Through With a Licensed Clinician
If you are weighing Ozempic against Mounjaro, or their weight-management siblings, a licensed online program connects you with a clinician who can review your medical history and, if appropriate, write a prescription through a legitimate pharmacy.
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The following published sources were used for the trial results, approval dates, and prescribing information referenced on this page. Always verify against the most current version of each document.
- Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). New England Journal of Medicine, 2025.
- Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). New England Journal of Medicine, 2021.
- US Food and Drug Administration. FDA Approves Novel, Dual-Targeted Treatment for Type 2 Diabetes (Mounjaro approval announcement), May 2022.
- Novo Nordisk. Ozempic (semaglutide) approved in the US, December 2017; Ozempic 2 mg dose approved, March 2022.
- Ozempic (semaglutide) US Prescribing Information, Novo Nordisk.
- Mounjaro (tirzepatide) US Prescribing Information, Eli Lilly.