Semaglutide (Wegovy, Ozempic) acts on one gut hormone receptor, GLP-1, while tirzepatide (Zepbound, Mounjaro) acts on two, GLP-1 and GIP. In SURMOUNT-5, the only published head-to-head trial in adults with obesity, people on tirzepatide lost an average of 20.2% of their body weight at 72 weeks, compared with 13.7% on semaglutide. Both are weekly injections with gradual step-ups, and both mainly cause nausea, diarrhea, vomiting and constipation. Which one fits you depends on your health, your goals, how you tolerate it and what is available and covered, and that is a choice to make with your clinician.
Key takeaways
- Semaglutide is a GLP-1 receptor agonist. Tirzepatide is a GIP and GLP-1 receptor agonist. Both slow stomach emptying and act on appetite areas of the brain.
- In SURMOUNT-5 (751 adults with obesity, no diabetes, 72 weeks), average weight change was -20.2% on tirzepatide (10 or 15 mg) vs -13.7% on semaglutide (1.7 or 2.4 mg). Waist size fell by about 7.2 in (18.4 cm) vs 5.1 in (13.0 cm).
- In their own placebo-controlled trials, Wegovy 2.4 mg averaged -14.9% at 68 weeks (STEP 1) and Zepbound averaged -15.0% to -20.9% at 72 weeks depending on dose (SURMOUNT-1).
- Gut side effects are the most common on both. In the label trials, nausea was reported by 44% on Wegovy 2.4 mg and 25% to 29% on Zepbound, but the labels warn that rates from different trials cannot be compared directly.
- Wegovy and Zepbound are approved for weight management. Ozempic and Mounjaro are approved for type 2 diabetes. In Mexico and much of Latin America, tirzepatide is sold as Mounjaro.
- Neither medicine is right for everyone. The choice is made with your clinician, based on your health history and how you respond.
How do semaglutide and tirzepatide work?
Both medicines copy gut hormones that your body releases after eating. Semaglutide activates the GLP-1 receptor. Tirzepatide is a single molecule that activates both the GLP-1 and the GIP receptors.
GLP-1 helps regulate appetite and how much you eat, slows how fast the stomach empties, and helps the pancreas release insulin when blood sugar is high. The Zepbound label says GIP may add to the regulation of food intake, based on nonclinical studies, and that both receptors are found in brain areas involved in appetite.
What this feels like day to day is similar on both: smaller portions feel enough, food noise gets quieter for many people, and the gut slows down. That last part is also why the side effects look so alike.
Which brand is which?
Two companies make these four brands. The active ingredient is what matters medically. The brand tells you the approved use.
| Brand | Ingredient | Maker | Form | US approved uses (adults unless noted) |
|---|---|---|---|---|
| Wegovy | Semaglutide | Novo Nordisk | Weekly injection, or daily tablet (US) | Weight management (also ages 12+ for the injection), lowering heart attack and stroke risk in people with heart disease and obesity or overweight, and a liver condition called MASH (injection) |
| Ozempic | Semaglutide | Novo Nordisk | Weekly injection, and a daily tablet in the US | Type 2 diabetes, lowering heart and kidney risk in type 2 diabetes |
| Zepbound | Tirzepatide | Eli Lilly | Weekly injection | Weight management, moderate to severe obstructive sleep apnea with obesity |
| Mounjaro | Tirzepatide | Eli Lilly | Weekly injection | Type 2 diabetes (also ages 10+), lowering heart attack and stroke risk in type 2 diabetes |
So "Wegovy vs Zepbound" is the semaglutide vs tirzepatide question for weight, and "Ozempic vs Mounjaro" is the same question for type 2 diabetes. The labels say not to combine either medicine with another GLP-1 medicine.
Which causes more weight loss, semaglutide or tirzepatide?
In the one head-to-head trial, tirzepatide led to more weight loss on average. SURMOUNT-5, published in the New England Journal of Medicine in 2025, randomly assigned 751 adults with obesity and without type 2 diabetes to the highest dose they could tolerate of tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg), injected weekly for 72 weeks.
| Trial | Who | Length | Average weight change |
|---|---|---|---|
| SURMOUNT-5 (head-to-head) | 751 adults, obesity, no diabetes | 72 weeks | Tirzepatide -20.2%, semaglutide -13.7% |
| STEP 1 (semaglutide vs placebo) | 1,961 adults, obesity or overweight, no diabetes | 68 weeks | Semaglutide 2.4 mg -14.9%, placebo -2.4% |
| SURMOUNT-1 (tirzepatide vs placebo) | 2,539 adults, obesity or overweight, no diabetes | 72 weeks | Tirzepatide 5 mg -15.0%, 10 mg -19.5%, 15 mg -20.9%, placebo -3.1% |
In SURMOUNT-5, that was an average of about 50 lb (22.8 kg) on tirzepatide vs about 33 lb (15.0 kg) on semaglutide, and people on tirzepatide were more likely to reach losses of 10%, 15%, 20% and 25%. Keep in mind that the trial was open-label, meaning participants knew which drug they were taking, and it was funded by Eli Lilly, the maker of tirzepatide.
Averages hide a wide range, and results vary a lot within each group. Your result depends on your dose, how long you stay on it, your starting point, and your health. Our weight timeline tool shows the trial curves over time.
The US Wegovy label now also lists a 7.2 mg weekly dose for some adults. In its 72-week trial in adults with obesity, average weight change was -18.8% on 7.2 mg, -15.5% on 2.4 mg and -3.9% on placebo. It has not been compared head to head with tirzepatide.
How do the side effects compare?
The side effects are the same kind on both: mostly gut symptoms, most common while the dose is being stepped up, and usually mild to moderate. These are the rates from each label's placebo-controlled weight trials.
| Side effect | Wegovy 2.4 mg | Zepbound 5 / 10 / 15 mg |
|---|---|---|
| Nausea | 44% (placebo 16%) | 25% / 29% / 28% (placebo 8%) |
| Diarrhea | 30% (placebo 16%) | 19% / 21% / 23% (placebo 8%) |
| Vomiting | 24% (placebo 6%) | 8% / 11% / 13% (placebo 2%) |
| Constipation | 24% (placebo 11%) | 17% / 14% / 11% (placebo 5%) |
| Any gut side effect | 73% (placebo 47%) | 56% at each dose (placebo 30%) |
| Stopped because of gut side effects | 4.3% (placebo 0.7%) | 1.9% / 3.3% / 4.3% (placebo 0.5%) |
| Hair loss | 3% (placebo 1%) | 5% / 4% / 5% (placebo 1%) |
Read this table with care. Both labels state that side effect rates from one drug's trials cannot be directly compared with another's, because the trials enrolled different people and counted events in different ways. Notice that placebo rates were also very different between the two programs.
The fairest comparison comes from SURMOUNT-5, where both drugs were given in the same trial. There, gut side effects were the most common on both, mostly mild to moderate and during dose escalation. Stopping because of gut side effects was reported in 5.6% on semaglutide and 2.7% on tirzepatide.
Both labels carry the same serious warnings: pancreatitis, gallbladder disease, kidney problems from dehydration, severe allergic reactions, low blood sugar with insulin or sulfonylureas, diabetic eye changes in people with type 2 diabetes, and food staying in the stomach during sedation. Both have a boxed warning about thyroid C-cell tumors seen in rodents, and neither should be used by people with a personal or family history of medullary thyroid cancer or MEN 2.
Contact your clinician or seek care for severe stomach pain that will not go away, pain spreading to your back, vomiting that stops you keeping fluids down, signs of an allergic reaction, or a lump in your neck, whichever medicine you take.
For more detail, see our guides to Wegovy and Ozempic side effects and GLP-1 side effects week by week.
How is the dosing schedule different?
Both are injected under the skin once a week, on the same day each week, at any time of day, with or without meals. Both start low and step up every 4 weeks to reduce gut side effects. The difference is the numbers and the number of steps.
| Semaglutide (Wegovy injection) | Tirzepatide (Zepbound) | |
|---|---|---|
| Starting dose on the label | 0.25 mg weekly for 4 weeks | 2.5 mg weekly for 4 weeks |
| Steps | 0.5 mg, 1 mg, 1.7 mg, every 4 weeks | Up in 2.5 mg steps, at least 4 weeks apart |
| Maintenance on the label | 2.4 mg (recommended) or 1.7 mg; up to 7.2 mg for some adults | 5 mg, 10 mg or 15 mg |
| Earliest week at maintenance | Week 17 | Week 5 (5 mg), later for higher doses |
| Half-life | About 1 week | About 5 to 6 days |
The diabetes brands follow a similar shape. Ozempic starts at 0.25 mg and goes up to a maximum of 2 mg. Mounjaro starts at 2.5 mg and goes up to a maximum of 15 mg in adults. Wegovy is also available in the US as a daily tablet that steps from 1.5 mg to 25 mg.
The labels also have rules for missed doses and for switching, and they differ between the two medicines. Follow your prescriber and the label for anything about missed doses, switching or stopping. You can compare the schedules in our titration schedules tool.
Can you get both in Latin America?
Brand names and approved uses depend on the country. Zepbound is a US brand name. In Mexico and much of Latin America, tirzepatide is sold as Mounjaro, and what it is approved for locally can differ from the US label. Semaglutide is sold as Ozempic and, in some countries, Wegovy. The Wegovy tablet and the Ozempic tablet described here are US products.
If you live outside the US, ask your clinician which brands are available where you live and what each is approved for there. The trial results above apply to the active ingredient, whatever the brand name on the box.
How do you decide between them?
You do not have to decide alone, and you should not. Your clinician weighs things this page cannot: your medical history, other medicines, conditions such as type 2 diabetes, sleep apnea or heart disease, how you have tolerated other treatments, and what is available and covered for you. Some people do well on the first one they try. Others change with their clinician's guidance.
Good questions to bring to your appointment:
- Which medicine and which approved use fits my situation?
- What side effects should I expect during the step-ups, and when should I call you?
- How will we judge whether it is working?
How Morning helps
Morning works the same way whichever medicine you use. It keeps a shot log with the dose plan you and your clinician set, sends shot-day reminders, and remembers your last injection sites. Side-effect check-ins show patterns around shot day, and weight charts sync with Apple Health, so your doctor report gives your clinician real data when you talk about how it is going.
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Questions
Is Zepbound the same as Mounjaro?
Yes, both are tirzepatide made by Eli Lilly. In the US, Zepbound is approved for weight management and sleep apnea with obesity, and Mounjaro for type 2 diabetes. In Mexico and much of Latin America, tirzepatide is sold as Mounjaro.
Is Wegovy the same as Ozempic?
Both are semaglutide made by Novo Nordisk. Wegovy is approved for weight management and heart risk reduction and goes up to 2.4 mg (7.2 mg for some adults). Ozempic is approved for type 2 diabetes and goes up to 2 mg.
Does tirzepatide cause more side effects than semaglutide?
Both mainly cause gut side effects during step-ups. The labels warn that rates from separate trials cannot be compared directly. In the head-to-head SURMOUNT-5 trial, 5.6% on semaglutide and 2.7% on tirzepatide stopped because of gut side effects.
How much more weight do people lose on tirzepatide?
In SURMOUNT-5, average weight change at 72 weeks was -20.2% on tirzepatide vs -13.7% on semaglutide, a difference of about 6.5 percentage points. Individual results vary widely in both groups.
Can I switch from semaglutide to tirzepatide?
Switching is a decision for your prescriber, who will set the starting dose and timing. Do not change medicines or doses on your own. Follow your prescriber and the label.
Sources
- Aronne LJ et al. Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5). N Engl J Med 2025;393:26-36
- Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med 2021;384:989-1002
- Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022;387:205-216
- American College of Cardiology journal scan of SURMOUNT-5 (weight in kg and discontinuation figures)
- Wegovy (semaglutide) injection and tablets, US prescribing information, DailyMed
- Zepbound (tirzepatide), US prescribing information, DailyMed
- Ozempic (semaglutide) injection, US prescribing information, DailyMed
- Mounjaro (tirzepatide), US prescribing information, DailyMed
Keep reading
Educational information, not medical advice. Talk to your clinician about your treatment.