Guides / Comparing and switching
Wegovy vs Zepbound
One is semaglutide, the other tirzepatide, and one trial has put them side by side.
[00] Short answer
- Wegovy is semaglutide (GLP-1). Zepbound is tirzepatide (GIP and GLP-1). Both are once-weekly injections approved for weight reduction1–2.
- In SURMOUNT-5, the only head-to-head trial, average weight change at 72 weeks was −20.2% on tirzepatide and −13.7% on semaglutide3.
- Nausea was about as common on both in that trial: 43.6% on tirzepatide and 44.4% on semaglutide. Vomiting was 15.0% vs 21.3%4.
- Wegovy steps up every 4 weeks from 0.25 mg to 2.4 mg (up to 7.2 mg). Zepbound starts at 2.5 mg and goes up to 15 mg1–2.
What's the difference between Wegovy and Zepbound?
Wegovy contains semaglutide, which acts on the GLP-1 receptor. Zepbound contains tirzepatide, which acts on both the GIP and GLP-1 receptors1–2. Both are approved in the US for weight reduction alongside diet and activity, and each has extra approved uses1–2.
| Wegovy | Zepbound | |
|---|---|---|
| Medicine | Semaglutide (Novo Nordisk)1 | Tirzepatide (Eli Lilly)2 |
| Other approved uses | Lowering heart attack and stroke risk in adults with heart disease and obesity or overweight; MASH with liver scarring; weight in teens 12+1 | Moderate to severe obstructive sleep apnea in adults with obesity2 |
| How often | Once a week (injection) or once a day (tablet)1 | Once a week2 |
| Half-life | About 1 week1 | About 5 to 6 days2 |
| Stopped because of side effects (label trials) | 6.8% on 2.4 mg vs 3.2% on placebo1 | 4.8%, 6.3% and 6.7% on 5, 10 and 15 mg vs 3.4% on placebo2 |
| Boxed warning | Thyroid C-cell tumors in rodents1 | Thyroid C-cell tumors in rats2 |
Which works better for weight loss, Wegovy or Zepbound?
In SURMOUNT-5, tirzepatide (the medicine in Zepbound) led to more weight loss than semaglutide (the medicine in Wegovy): an average of 20.2% of body weight vs 13.7% after 72 weeks3. Waist size fell by an average of 18.4 cm vs 13.0 cm3.
- 751 adults with obesity and without type 2 diabetes took part. It was open-label, so people knew which medicine they were on3.
- Each person took the highest dose they tolerated: tirzepatide 10 mg or 15 mg, or semaglutide 1.7 mg or 2.4 mg, once a week3.
- The trial was funded by Eli Lilly, which makes tirzepatide, and several authors work for Lilly3.
| Result | Tirzepatide (10–15 mg) | Semaglutide (1.7–2.4 mg) |
|---|---|---|
| Average weight change | −20.2% | −13.7% |
| Lost 10% or more | 87.7% | 66.7% |
| Lost 15% or more | 71.7% | 45.0% |
| Lost 20% or more | 55.0% | 31.1% |
| Lost 25% or more | 36.5% | 18.6% |
| Lost 30% or more | 23.0% | 8.2% |
| Average waist change | −18.4 cm | −13.0 cm |
| Comparing only 15 mg vs 2.4 mg | −21.8% | −15.4% |
All figures from the trial's posted results4. These are group averages and shares. They don't predict what one person will lose.
Wegovy's 7.2 mg dose wasn't part of SURMOUNT-5. For how 7.2 mg did against 2.4 mg, see Wegovy 7.2 mg.
Wegovy vs Zepbound side effects: which is easier to tolerate?
In SURMOUNT-5, the most common side effects were stomach and gut effects on both medicines, mostly mild to moderate and mainly while the dose was going up3. Nausea, diarrhea and constipation were reported at similar rates. Vomiting and acid reflux were more common on semaglutide, and injection site reactions on tirzepatide4.
| Event | Tirzepatide | Semaglutide |
|---|---|---|
| Nausea | 43.6% (163) | 44.4% (167) |
| Constipation | 27.0% (101) | 28.5% (107) |
| Diarrhea | 23.5% (88) | 23.4% (88) |
| Vomiting | 15.0% (56) | 21.3% (80) |
| Fatigue | 10.4% (39) | 12.2% (46) |
| Acid reflux (GERD) | 6.1% (23) | 10.6% (40) |
| Injection site reaction | 8.6% (32) | 0.3% (1) |
| Hair loss | 8.3% (31) | 6.1% (23) |
| Serious adverse events (any) | 4.8% (18) | 3.5% (13) |
Counts from the posted results, which list events reported in at least 5% of either group4. Six people in each group left the trial because of an adverse event4.
The labels have their own numbers from placebo-controlled trials. Nausea was 44% on Wegovy 2.4 mg vs 16% on placebo, and 25% to 29% on Zepbound 5 mg to 15 mg vs 8% on placebo1–2. Those come from separate trials, and both labels say rates can't be directly compared across drugs1–2. The head-to-head numbers above are the fairer comparison.
More on what helps and how long it lasts: GLP-1 side effects.
Wegovy vs Zepbound dosing: steps and timing
Both are injected once a week and both start low. Wegovy starts at 0.25 mg and steps up every 4 weeks to 2.4 mg at week 17. Zepbound starts at 2.5 mg for 4 weeks, then 5 mg, with optional 2.5 mg steps after at least 4 weeks1–2.
| Weeks | Wegovy injection | Zepbound |
|---|---|---|
| 1 to 4 | 0.25 mg | 2.5 mg |
| 5 to 8 | 0.5 mg | 5 mg |
| 9 to 12 | 1 mg | 5 mg, or 7.5 mg if stepping up |
| 13 to 16 | 1.7 mg | Continue, or next 2.5 mg step |
| 17 onward | 2.4 mg (or 1.7 mg); 7.2 mg possible after 4+ weeks on 2.4 mg | Steps continue as needed to 5, 10 or 15 mg; 15 mg is week 21 at the earliest |
Zepbound steps are 'may increase' after at least 4 weeks on each dose, so the week numbers vary from person to person.
| Wegovy injection | Zepbound | |
|---|---|---|
| Missed dose | Take it if the next dose is more than 2 days away1 | Take within 4 days (96 hours)2 |
| 2 or more missed in a row | Restart the step-up at a lower dose1 | No separate rule in the label |
| Pens and vials | Single-dose pens and syringes, a 4-dose 2.4 mg FlexTouch pen, and daily tablets1 | Single-dose pens and vials, 4-dose vials and KwikPens2 |
Wegovy vs Mounjaro for weight loss in the UK
In the UK, the Zepbound name isn't used. Tirzepatide for weight management is prescribed as Mounjaro, and semaglutide as Wegovy5–7. Both are licensed for adults with a BMI of 30 or more, or 27 to 30 with a weight-related condition5–6.
- UK Wegovy: 0.25 mg rising over 16 weeks to 2.4 mg, with 7.2 mg possible for adults with obesity after at least 4 weeks on 2.4 mg5.
- UK Mounjaro: 2.5 mg for 4 weeks, then 5 mg, with 2.5 mg steps after at least 4 weeks, up to 15 mg6.
- Both SmPCs say to decide whether to continue if you haven't lost at least 5% of your starting weight after 6 months (for Mounjaro, 6 months after reaching your highest tolerated dose)5–6.
Questions
Is Zepbound stronger than Wegovy?
Their mg doses can't be compared because they're different medicines. In the SURMOUNT-5 trial, average weight loss at 72 weeks was 20.2% on tirzepatide (Zepbound's medicine) and 13.7% on semaglutide (Wegovy's medicine).
Does Zepbound cause less nausea than Wegovy?
In SURMOUNT-5 nausea was about the same: 43.6% on tirzepatide and 44.4% on semaglutide. Vomiting was less common on tirzepatide, 15.0% vs 21.3%. Injection site reactions were more common on tirzepatide, 8.6% vs 0.3%.
Did SURMOUNT-5 test Wegovy 7.2 mg?
No. People on semaglutide took 1.7 mg or 2.4 mg a week, whichever was the highest dose they tolerated. The Wegovy label describes separate 72-week trials that compared 7.2 mg with 2.4 mg and placebo.
Who funded the Wegovy vs Zepbound trial?
Eli Lilly, which makes tirzepatide (Zepbound). It was an open-label trial, meaning people knew which medicine they were taking.
Which one is approved for heart risk or sleep apnea?
In the US, Wegovy is approved to lower the risk of heart attack and stroke in adults with heart disease and obesity or overweight. Zepbound is approved for moderate to severe obstructive sleep apnea in adults with obesity.
Is Zepbound sold in the UK?
Not under that name. In the UK, tirzepatide for weight management is Mounjaro. Semaglutide for weight management is Wegovy.
Sources
Checked against Wegovy US prescribing information (revised 06/2026), Zepbound US prescribing information (revised 08/2026), the SURMOUNT-5 trial (NEJM 2025) and its posted results on ClinicalTrials.gov, and the UK Wegovy and Mounjaro SmPCs. How we check
- 1Wegovy (semaglutide) injection and tablets, US prescribing information, sections 1, 2.2, 2.4, 3, 6.1 and 12.3. Novo Nordisk, revised 06/2026; Tables 1 and 3
- 2Zepbound (tirzepatide) US prescribing information, sections 1, 2.1 to 2.3, 3, 6.1 and 12.3. Eli Lilly, revised 08/2026; Table 1
- 3Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). N Engl J Med 2025;393:26-36. PubMed 40353578; abstract
- 4SURMOUNT-5 (NCT05822830): posted results, outcome measures, participant flow and adverse events. ClinicalTrials.gov. accessed 8 Nov 2026
- 5Wegovy FlexTouch solution for injection in pre-filled pen, UK SmPC, sections 4.1 and 4.2. eMC, updated 22 Sep 2026
- 6Mounjaro KwikPen solution for injection in pre-filled pen, UK SmPC, sections 4.1 and 4.2. eMC, updated 8 Sep 2026
- 7MHRA: GLP-1 medicines for weight loss and diabetes: what you need to know (GOV.UK). updated 5 Feb 2026
This guide explains what labels and published studies say. It isn't medical advice and doesn't replace your prescriber or pharmacist.
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Read next
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- Mounjaro vs ZepboundSame medicine, same doses, same pens and vials. The difference is what each one is approved for, and in the UK there's only Mounjaro.
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