Mounjaro vs Wegovy
Tirzepatide vs semaglutide, side by side: how they work, the dose schedules, pens, storage, NHS access and the head-to-head trial results.
Updated 30 October 2026
| Mounjaro | Wegovy | |
|---|---|---|
| Active ingredient | tirzepatide | semaglutide |
| Drug class | Dual GIP + GLP-1 | GLP-1 |
| How often | Once a week | Once a week |
| Licensed in the UK for | Weight management (also type 2 diabetes) | Weight management |
| Pen | KwikPen | FlexTouch |
| Starting dose | 2.5 mg | 0.25 mg |
| Maintenance dose | 5, 10 or 15 mg | 2.4 mg (optional 7.2 mg) |
| Highest dose | 15 mg | 7.2 mg |
| Storage once in use | Up to 30 days below 30 °C | Up to 6 weeks below 30 °C |
| Average weight loss in trials | about 21% (SURMOUNT-1, 72 weeks (15 mg)) | about 15% (STEP-1, 68 weeks (2.4 mg)) |
| Trial figures are averages over the whole study, at the top dose. Real-world results vary. | ||
| NHS availability | On NHS weight-management pathways (criteria apply) | Via specialist NHS weight-management services |
Head to head
In SURMOUNT-5, the first head-to-head trial, average weight loss over 72 weeks was 20.2% with tirzepatide versus 13.7% with semaglutide. It was an open-label trial funded by the maker of tirzepatide. SURMOUNT-5 (NEJM).
Thinking of switching?
There’s no simple dose-for-dose swap between these; they’re different medicines. A switch means starting the new one at its lowest dose and titrating up again, under your prescriber. People’s experience of switching varies a lot, so the GLP-1 communities are worth a read for the lived side.
Facts from the UK SmPCs (Mounjaro, Wegovy) and the trials linked above.
This compares the facts; it doesn’t say which is right for you. That’s a decision for you and your prescriber.
Common questions
- Is Mounjaro better than Wegovy for weight loss?
- In SURMOUNT-5, the first head-to-head trial, average weight loss over 72 weeks was 20.2% with tirzepatide (Mounjaro) versus 13.7% with semaglutide (Wegovy). It was an open-label trial funded by the maker of tirzepatide, and averages don’t predict any one person’s result. Which is right for you is a decision for you and your prescriber.
- What’s the difference between Mounjaro and Wegovy?
- Mounjaro is tirzepatide, which acts on two gut hormones (GIP and GLP-1); Wegovy is semaglutide, which acts on one (GLP-1). Both are once-weekly injections licensed for weight management in the UK, but they have different pens, dose steps and storage rules.
- Can I switch from Wegovy to Mounjaro?
- There’s no simple dose-for-dose swap; they’re different medicines. Switching means starting Mounjaro at its lowest dose (2.5 mg) and titrating up again, under your prescriber.
- How do the doses compare?
- Mounjaro starts at 2.5 mg weekly and goes to a 5, 10 or 15 mg maintenance. Wegovy steps 0.25 → 0.5 → 1 → 1.7 → 2.4 mg over 16 weeks, with an optional 7.2 mg. See the dose-schedule tools for the dated step-up.