Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow Mounjaro and Wegovy compare, and what the trial data says about switching
What SURMOUNT-5 actually showed about these two medicines side by side
For a long time, the comparison between tirzepatide and semaglutide rested on indirect modelling, different trials, different populations, different designs. SURMOUNT-5 changed that. In this open-label, randomised trial of 751 adults living with obesity and without type 2 diabetes, participants received either tirzepatide or semaglutide 2.4mg weekly for 72 weeks. Tirzepatide produced a meaningfully greater average reduction in body weight. The underlying trial data from the wider SURMOUNT programme had already shown around 20–21% average weight loss at the 15mg dose; SURMOUNT-5 added the direct comparison that practitioners and patients had been waiting for.
The difference comes partly from mechanism. Wegovy works on a single receptor pathway (GLP-1) influencing appetite and gastric emptying. Mounjaro activates two: GIP and GLP-1. Whether that dual action accounts for the gap in outcomes, or whether individual response matters more, remains a question the trials can't fully answer for any one person, and our detailed look at Mounjaro va Wegovy works through those nuances if you want to explore them further. If you've been on Wegovy and your results have plateaued, the evidence gives a clinical rationale for discussing a switch, but it's the prescriber's assessment of your full picture that settles it.
One misconception worth setting aside: some people assume that because both medicines are injected once weekly and cause similar early side effects, they're essentially interchangeable and the switch is trivial. They're meaningfully different in structure, and if you're thinking about moving from Mounjaro to Wegovy, or indeed in the other direction, our guide to switching from Mounjaro to Wegovy explains what that transition involves clinically, including how to time the first Mounjaro dose relative to your last Wegovy injection.
A factual comparison: Mounjaro versus Wegovy
The table below draws on the licensed UK product information and published trial evidence. Numbers are cited where they derive from specific studies. Both medicines carry a Black Triangle (▼) designation from the MHRA, reflecting ongoing post-approval safety monitoring.
| Feature | Mounjaro (tirzepatide) | Wegovy injection (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP and GLP-1 receptor agonist | GLP-1 receptor agonist |
| Dosing range | 2.5mg to 15mg weekly | 0.25mg to 2.4mg weekly (up to 7.2mg approved Apr 2026) |
| Average weight loss (pivotal trial) | ~20–21% at 15mg over 72 weeks (SURMOUNT-1, NEJM) | ~15% at 2.4mg over 68 weeks (STEP 1, NEJM) |
| Head-to-head result | Greater average reduction (SURMOUNT-5, NEJM 2025) | Compared directly in SURMOUNT-5; lower average reduction |
| UK weight-loss licence | BMI ≥30, or ≥27 with a weight-related condition | BMI ≥30, or ≥27 with a weight-related condition |
| NICE appraisal | TA1026 (Dec 2024, updated Sep 2025) | TA875 (Mar 2023), max 2 years, specialist services |
For more detail on how these two medicines sit against each other across a wider range of factors, our Wegovy v Mounjaro page covers the nuances in full. A closer look at the specific cost difference is on the why Wegovy tends to cost less than Mounjaro page.
What a switch from Wegovy back to Mounjaro involves in practice
If you started on Mounjaro, moved to Wegovy for supply or cost reasons, and are now considering returning, the clinical process is the same as any medicine switch. The prescriber will want to know your current dose, how long you've been on Wegovy, what's driving the switch (insufficient results, side-effect profile, preference, availability) and whether your weight-related conditions have changed. Evidence of your current treatment is part of that review.
Going back to Mounjaro after Wegovy isn't simply a matter of restarting where you left off. Titration decisions and where in the Mounjaro dose schedule you begin will depend on your individual tolerance and clinical history. That's a conversation for a prescriber, not a search result.
At nume, our clinical team (which you can read about here) reviews every case individually before any treatment or switch is approved. The way we work means there are no automated approvals and no repeat prescriptions issued without clinical re-review. If you're already on Wegovy through another provider and want a second clinical perspective on whether Mounjaro might suit you better, a new consultation at our treatment page is the starting point.
The NHS access picture also affects some of these decisions. NICE's appraisal of tirzepatide (TA1026) set out phased NHS eligibility criteria; privately, neither a long wait nor a strict comorbidity list applies, eligibility is based on the licensed criteria and your prescriber's assessment. If you'd like a broader overview before deciding, the weight-loss treatment overview sets out the landscape.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.