Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow tirzepatide and semaglutide differ — and what the evidence shows
Step 1: understand what each molecule actually does
Semaglutide, the active ingredient in Wegovy, targets a single gut-hormone receptor called GLP-1. Activating that receptor reduces appetite, slows how quickly food leaves the stomach, and nudges the brain's fullness signals. It has been used in diabetes medicine for years before the higher 2.4mg weight-management dose was licensed.
Tirzepatide, sold as Mounjaro, activates two receptors: GLP-1 and GIP. GIP is a separate gut hormone that also plays a role in appetite and energy storage. This dual action is why Mounjaro is described as a dual agonist. No other weight-loss medicine licensed in the UK shares that mechanism. The NHS medicines page on tirzepatide covers how it works in accessible language if you want more detail.
A common misconception worth addressing: many people assume Mounjaro is just a stronger version of Ozempic, and if you are wondering whether Mounjaro is similar to Wegovy, the two medicines share some overlap but are structurally distinct molecules targeting overlapping but not identical pathways. Ozempic itself is also semaglutide, but licensed for type 2 diabetes rather than weight management, so it should not be conflated with Wegovy even though the active ingredient is the same.
Step 2: compare the clinical evidence side by side
Both medicines have strong trial programmes, but the results are not identical. SURMOUNT-1 (tirzepatide, 72 weeks) showed an average body-weight reduction of around 20–21% at the 15mg dose, published in the New England Journal of Medicine. STEP 1 (semaglutide 2.4mg, 68 weeks) showed an average reduction of around 15%.
Those trials ran separately against placebo, so direct comparison is tricky. The SURMOUNT-5 study addressed that directly: in an open-label head-to-head trial of 751 adults with obesity and no diabetes over 72 weeks, tirzepatide produced greater average weight reduction than semaglutide 2.4mg. NICE's appraisal of tirzepatide, TA1026, acknowledges that indirect comparisons favour tirzepatide, while noting the evidence continues to mature.
Wegovy also now has a 7.2mg dose approved by the MHRA (April 2026), with trial data showing around 20.7% average weight loss over 72 weeks, narrowing the gap with tirzepatide's highest dose considerably. The landscape is still moving.
| Feature | Mounjaro (tirzepatide) | Wegovy injection (semaglutide) |
|---|---|---|
| Active ingredient | Tirzepatide | Semaglutide |
| Receptor target | GLP-1 + GIP (dual agonist) | GLP-1 only |
| UK weight-loss licence | Yes (BMI ≥30, or ≥27 + condition) | Yes (BMI ≥30, or ≥27 + condition) |
| Maintenance doses available | 5, 7.5, 10, 12.5, 15mg | 1.7, 2.4, 7.2mg |
| Average weight loss (highest dose, trial data) | ~20–21% at 15mg (SURMOUNT-1, NEJM) | ~15% at 2.4mg (STEP 1, NEJM); ~20.7% at 7.2mg |
| Administration | Once-weekly subcutaneous injection | Once-weekly subcutaneous injection |
Step 3: check which medicines are actually licensed for weight loss in the UK
This matters more than most people realise. Wegovy is licensed for weight management. Ozempic contains the same semaglutide molecule but holds a licence for type 2 diabetes only, it is not approved as a weight-loss medicine in the UK, and the MHRA is explicit on this point. Prescribing it for weight loss would be off-label. Rybelsus is also oral semaglutide, again licensed for diabetes, not weight management.
Mounjaro is licensed for both weight management and type 2 diabetes in the UK. So when someone asks whether semaglutide is the same as Mounjaro, the short answer is: different molecule, partly overlapping licence, meaningfully different mechanism. If you want a fuller breakdown of semaglutide versus tirzepatide across both pillars, that page covers the detail.
Side-effect profiles overlap considerably, nausea, changes in bowel habits, reduced appetite and some injection-site reactions appear with both. The NHS semaglutide medicines page lists the semaglutide-specific profile; the tirzepatide page covers Mounjaro's. Tolerability varies between individuals, which is one more reason the choice is a clinical one.
Step 4: how to reach the right decision for you
No responsible comparison page can tell you which medicine suits you. Prescribers look at your BMI, any weight-related conditions, your medical history, medicines you already take, and your own preferences. If you are also asking whether Mounjaro is semaglutide, the answer shapes that decision, and the Mounjaro or semaglutide: which is better page goes into more clinical nuance on it.
At nume, every consultation is reviewed by a named GPhC-registered prescriber, you can meet our clinical team here. We're a GPhC-registered pharmacy (premises registration 9012878, verifiable at the GPhC register). Which medicine is right for you is a decision our prescribers make with you, not one an algorithm (or a comparison table) can make alone. Start your free consultation to begin that conversation.
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