Mounjaro®
Starting from £179.99/mo
Start journey Learn moreMounjaro vs Wegovy: what the evidence says and how to choose
What the SURMOUNT-5 head-to-head trial found
The most direct comparison available comes from SURMOUNT-5, a 72-week open-label trial of 751 adults with obesity and no diabetes. Participants received either tirzepatide or semaglutide 2.4mg alongside lifestyle guidance. Tirzepatide produced meaningfully greater average weight reduction, a finding that NICE's appraisal of tirzepatide (TA1026) acknowledged when noting that indirect comparisons favour tirzepatide over semaglutide 2.4mg. The gap was not trivial, though both medicines produced clinically significant weight loss in trial participants.
SURMOUNT-1 also put the scale of tirzepatide's effect in context: at the 15mg dose over 72 weeks, average body-weight reduction was around 20–21%. Wegovy at 2.4mg achieved roughly 15% average reduction in the STEP 1 trial over 68 weeks. These figures are from different trials with different populations, so a direct percentage comparison carries caveats, and our page exploring whether Wegovy is as strong as Mounjaro works through exactly what those differences mean in practice. A dedicated look at semaglutide versus tirzepatide head-to-head data explains those caveats in more detail.
One further consideration: Novo Nordisk's higher-dose 7.2mg Wegovy pen, approved by the MHRA in April 2026, reported around 20.7% average weight loss over 72 weeks in trials. That narrows the gap with tirzepatide's highest dose considerably. It is a newer option and not yet as widely studied as 2.4mg.
How the two medicines work differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. It activates two gut-hormone pathways involved in appetite regulation and blood-sugar control. Wegovy (semaglutide) acts on a single pathway, the GLP-1 receptor only. The dual mechanism is one reason researchers believe tirzepatide achieves higher average reductions, though the biology varies between individuals. The NHS tirzepatide medicines page describes how the drug works at a patient level, without jargon.
Both medicines slow gastric emptying and reduce appetite, and both are once-weekly subcutaneous injections via pre-filled pen. Mounjaro comes in six UK doses from 2.5mg up to 15mg; Wegovy's standard pathway runs from 0.25mg up to 2.4mg (or 7.2mg with the new pen). Treatment begins at a low starter dose in both cases to let your system adjust before the prescriber moves things up. Neither medicine is a quick fix, both work best alongside changes to eating and activity habits, and the prescriber discussion matters as much as the medicine itself.
If you are weighing up how the safety profiles compare alongside the efficacy data, our page on whether Wegovy is safer than Mounjaro covers the side-effect evidence in detail. The short version: both share a broadly similar, GI-led tolerability picture.
Side-by-side: what the numbers look like
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist only |
| UK maintenance dose | Up to 15mg weekly | Up to 2.4mg (or 7.2mg) weekly |
| Average weight loss in pivotal trial | ~20–21% at 15mg (SURMOUNT-1, 72 wks) | ~15% at 2.4mg (STEP 1, 68 wks); ~20.7% at 7.2mg |
| NICE recommendation | TA1026 (Dec 2024, updated Sep 2025) | TA875 (Mar 2023) |
| Licensed weight-loss use in UK | Yes (also type 2 diabetes) | Yes (also CV risk reduction; MASH from Jul 2026) |
A note on what is not in this table: Ozempic and Rybelsus are both semaglutide, but neither is licensed for weight management in the UK, they are prescribed for type 2 diabetes. Reading about semaglutide for weight loss means Wegovy specifically. Our broader Wegovy vs Mounjaro comparison covers additional practical differences worth reading before you decide.
Which one is right for you?
Average trial figures are useful context, but your prescriber is looking at more than a percentage. Your medical history, any existing conditions, how your body tolerates the starter dose, what other medicines you take, all of this shapes which treatment makes clinical sense. Tirzepatide produces higher average losses at the population level, and NICE's TA1026 reflects that. But for a meaningful number of people, semaglutide is the right clinical choice. One thing worth doing before your consultation: check your BMI using the NHS BMI calculator, it takes under a minute and means your prescriber can move straight to the clinical conversation.
If you have already been on one and are considering switching, the specifics of transitioning from Mounjaro to Wegovy and what to expect are worth understanding first. If cost is part of the equation, our pricing comparison for Wegovy and Mounjaro walks through what private treatment typically costs and why the numbers differ between providers.
Which suits you is a clinical decision our prescribers make with you, based on your full health picture, not a league table.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.