Mounjaro®
Starting from £179.99/mo
Start journey Learn moreComparing Mounjaro and Wegovy through the lens of SURMOUNT-5: what the evidence means for your decision
What the SURMOUNT-5 trial actually measured — and what it didn't
SURMOUNT-5 randomised 751 adults with obesity (BMI ≥30, or ≥27 with at least one weight-related condition) who did not have type 2 diabetes. Half received tirzepatide, titrated up to 15mg weekly; half received semaglutide 2.4mg weekly. Both groups followed a reduced-calorie diet and increased their activity levels. The trial ran for 72 weeks.
Tirzepatide produced meaningfully greater average weight loss across the trial period. The detailed results from SURMOUNT-5 show roughly 20% average body-weight reduction with tirzepatide versus around 14% with semaglutide 2.4mg, a gap that held across the main subgroups. NICE's appraisal of tirzepatide, TA1026 published December 2024, references indirect comparisons that also favour tirzepatide.
One thing worth clearing up quietly: SURMOUNT-5 compared tirzepatide against the 2.4mg maintenance dose of Wegovy, not the newer 7.2mg dose approved by the MHRA in early 2026. The 7.2mg dose narrows the gap in separate trials. That distinction matters when you read confident headlines declaring tirzepatide the permanent winner, the evidence picture is still developing. If you want to understand how these two medicines compare more broadly, our Wegovy vs Mounjaro overview covers the key differences alongside the clinical data, and our cost comparison page covers the financial side specifically.
How tirzepatide and semaglutide differ mechanically, and why it matters in practice
Semaglutide (Wegovy) works on a single receptor pathway: GLP-1, which slows stomach emptying and reduces appetite. Tirzepatide (Mounjaro) activates both GLP-1 and GIP receptors simultaneously, making it the only dual-agonist weight-loss medicine licensed in the UK. The NHS tirzepatide medicines page explains the dual mechanism in plain terms.
In practice, the difference shows up in the magnitude of appetite reduction and, for many people, in how quickly the body adapts to each medicine. Neither is comfortable for everyone at the start. Both share a GI-led side-effect profile: nausea, loose stools, and indigestion are most common in the first weeks after starting or increasing the dose, then typically settle. The clinical profile of each treatment (including which conditions in your history might favour one over the other) is exactly what our clinical team weighs during a consultation.
Storage and format are identical in principle: once-weekly subcutaneous injection, pre-filled pen, refrigerated between doses. Specific room-temperature windows differ between the two; the Patient Information Leaflet for each medicine is the definitive reference for those details, not general content like this.
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide 2.4mg) |
|---|---|---|
| Receptor pathway | Dual: GLP-1 and GIP | Single: GLP-1 |
| Average weight loss (SURMOUNT-5 / STEP 1) | ~20% at 72 weeks (tirzepatide 15mg)* | ~15% at 68 weeks (semaglutide 2.4mg)** |
| UK licence for weight management | Yes (BMI ≥30, or ≥27 + condition) | Yes (BMI ≥30, or ≥27 + condition) |
| Highest approved maintenance dose (UK) | 15mg weekly | 7.2mg weekly (MHRA approved April 2026) |
| NICE-recommended for NHS | Yes (TA1026 (Dec 2024) | Yes) TA875 (Mar 2023, specialist services) |
| Starting dose | 2.5mg weekly | 0.25mg weekly |
*SURMOUNT-5, NEJM 2025. **STEP 1 trial, NEJM 2021. Figures are trial averages; individual results vary. Neither Ozempic nor Rybelsus is licensed for weight management in the UK, those are semaglutide products for type 2 diabetes. More on the Ozempic distinction here.
Which one fits your situation, and how the decision actually gets made
SURMOUNT-5 tells us tirzepatide produced greater average weight reduction in the population it studied. It does not tell us which medicine is right for you. The factors that shape a prescriber's recommendation include your BMI, existing health conditions, any medicines you already take, your history with weight-loss treatment, and your own preferences about injection experience and titration pace.
Some people do better on semaglutide. Some can't tolerate one but manage the other well. The trial averages describe a group; your consultation is about you. Thinking through which might suit you is a reasonable place to start, but the clinical call sits with a prescriber who can see your full picture.
If you're curious how the broader evidence (beyond SURMOUNT-5) stacks up between the two, this comparison of the two medicines draws on the wider trial data. You can also explore our treatment overview to see both options side by side. When you're ready, checking your eligibility with our prescribing team takes a few minutes and costs nothing.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.