Mounjaro®
Starting from £179.99/mo
Start journey Learn moreWhat the evidence actually shows — and what it leaves open
The head-to-head trial: what SURMOUNT-5 found
For years, comparing Mounjaro and semaglutide meant stitching together results from separate trials run at different times, in different populations. SURMOUNT-5 changed that. Published in the New England Journal of Medicine in 2025, it randomised 751 adults with obesity and no type 2 diabetes to either tirzepatide or semaglutide 2.4mg weekly for 72 weeks. Tirzepatide produced a meaningfully larger average weight reduction. NICE's appraisal of tirzepatide (TA1026) acknowledged the same finding, noting that indirect comparisons across trials consistently pointed in the same direction.
The mechanism behind the gap is plausible. Mounjaro activates both GIP and GLP-1 receptors; Wegovy (the semaglutide injection licensed for weight loss) targets GLP-1 alone. Activating two pathways that regulate appetite and blood sugar appears to produce a larger effect for most people. You can read more about how the two medicines differ biologically on our Mounjaro vs Wegovy mechanism of action page.
A question our prescribers hear most weeks is whether this means Mounjaro is simply the better medicine. The honest answer is that the trial average does not tell you what will happen to you specifically. Some people tolerate semaglutide better; some reach their goals with it; some have a clinical reason to prefer one over the other.
Where semaglutide closes the gap
The gap between the two medicines is not static. Novo Nordisk's 7.2mg semaglutide dose, approved by the MHRA in January 2026 and available as a dedicated single-dose pen from April 2026, produced around 20.7% average weight loss over 72 weeks in trials — considerably closer to tirzepatide's top-dose results than 2.4mg managed. Eligibility for the 7.2mg dose requires a BMI of 30 or above, and the titration schedule still starts at 0.25mg, with the prescriber guiding each step upward.
Semaglutide also holds additional UK authorisations that tirzepatide does not yet have: a licensed indication for reducing major cardiovascular event risk in eligible adults, and (from July 2026) conditional approval for a form of fatty liver disease called MASH. For someone with obesity and established cardiovascular disease, that broader evidence base may be clinically relevant. Mounjaro remains the only dual-agonist weight-loss medicine currently licensed in the UK.
For a closer look at how costs compare between the two treatments, the Wegovy vs Mounjaro cost page covers what drives the pricing differences.
How the two medicines compare at a glance
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide 2.4mg / 7.2mg) |
|---|---|---|
| Receptor targets | GIP and GLP-1 (dual agonist) | GLP-1 only |
| Average weight loss at top maintenance dose (72 weeks, clinical trials) | ~20–22% (SURMOUNT-1; NEJM) | ~15% at 2.4mg (STEP 1); ~20.7% at 7.2mg |
| Head-to-head result vs the other | Greater average loss (SURMOUNT-5, NEJM 2025) | Lower average loss at 2.4mg; narrows at 7.2mg |
| UK weight-loss licence | BMI ≥30, or ≥27 with a weight-related condition | BMI ≥30, or ≥27 with a weight-related condition |
| Additional UK indications | Type 2 diabetes management | Cardiovascular risk reduction; MASH (Jul 2026) |
| Oral option available? | No (injection only) | Yes, Wegovy tablets approved Jun 2026 (25mg maintenance) |
Note: Ozempic is also semaglutide but is licensed for type 2 diabetes management, not weight loss. It should not be sought for weight management. The Mounjaro vs Ozempic page explains the distinction clearly.
Side-effect profile and who might prefer which
Both medicines share a largely gastrointestinal side-effect profile: nausea, loose stools, constipation, indigestion and fatigue are the most commonly reported, typically most noticeable at the start of treatment or after a dose increase, and often settling over days to a couple of weeks. The NHS tirzepatide page and the equivalent semaglutide page list these in full.
Prescribers generally find that tolerability varies individually. Someone who struggled with nausea on semaglutide does not necessarily respond the same way to tirzepatide, and vice versa. People using oral contraceptives should know that tirzepatide may reduce pill absorption during the first four weeks of treatment and for four weeks after each dose increase, adding a barrier method during those windows is advised. There is no equivalent evidence of the same interaction with semaglutide.
Which medicine suits your profile is precisely the question a prescriber answers by reviewing your health history. Our clinical team does that review the same day you apply. If you want to explore the broader question of how the two medicines compare in practice, the Wegovy vs Mounjaro overview covers more ground, and the does tirzepatide work better than semaglutide page goes deeper into the evidence. Which suits you is a clinical decision our prescribers make with you, start your free consultation to begin that conversation.
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