SURMOUNT-5 head-to-head: tirzepatide vs semaglutide weight loss results

You've read the headlines. Here's what the trial measured

Imagine you've spent an evening reading about tirzepatide and semaglutide and you're still not sure which one the evidence actually favours. SURMOUNT-5 was designed to answer exactly that. Seven hundred and fifty-one adults with a BMI of 30 or above (or 27 or above with at least one weight-related condition) and no type 2 diabetes were randomised to either tirzepatide (at the highest tolerated dose up to 15 mg weekly) or semaglutide 2.4 mg weekly, for 72 weeks.

The primary endpoint was percentage body-weight change from baseline. Tirzepatide participants lost around 20% of body weight on average; the semaglutide arm lost around 14%. That is not a trivial gap. NICE's appraisal of tirzepatide (TA1026) notes that indirect comparisons across separate trials had already suggested tirzepatide performed better, and SURMOUNT-5 gave the first direct, controlled confirmation of that picture.

One practical thing worth doing before your consultation: spend sixty seconds on the NHS BMI calculator to confirm your current BMI figure. Your prescriber will ask, and having it to hand means the clinical conversation can move straight to the medicine question rather than circling back.

Both medicines are dual-pathway or single-pathway GLP-1 treatments that slow gastric emptying and reduce appetite. Tirzepatide is the only one that also activates GIP receptors, which may partly explain the additional weight loss. If you are curious what those differences look like in practice, our page on Ozempic 8 week weight loss before and after compared with Mounjaro gives a grounded sense of how the timelines and results tend to play out. The trial did not test doses above 2.4 mg for semaglutide, a relevant point given what came later (see below).

The comparison at a glance

Numbers from a single trial need context, so the table below sets the main SURMOUNT-5 findings alongside the licensed UK strengths, trial populations and NICE eligibility criteria for each medicine. It is a summary to inform discussion, not a prescription.

The full Wegovy vs Mounjaro breakdown on our site covers mechanism, eligibility and practical differences in more depth, if you want to compare the two medicines beyond what a single trial captures.

Where semaglutide is closing the gap, and what SURMOUNT-5 didn't test

SURMOUNT-5 compared tirzepatide against the 2.4 mg semaglutide dose that was standard at the time. Since then, the MHRA approved a 7.2 mg semaglutide maintenance dose, first announced in January 2026, with a dedicated single-dose pen approved on 14 April 2026. Early data for that higher dose reported average weight loss of around 20.7% over 72 weeks, which sits much closer to tirzepatide 15 mg territory. SURMOUNT-5's headline gap may narrow in future head-to-head work that includes the 7.2 mg arm.

There is also the newer oral option. The MHRA approved Wegovy tablets (oral semaglutide, 25 mg maintenance) in June 2026, the first oral GLP-1 licensed for weight management in the UK. Trial data showed around 13.6% average weight loss at 64 weeks. For people who prefer not to inject, that is a clinically meaningful alternative, even if the percentage sits below tirzepatide's trial figures. Our page on weight loss on Wegovy versus Mounjaro covers all three formulations together.

A few things SURMOUNT-5 cannot tell you: how you specifically will respond, which side-effect profile will suit your lifestyle, whether you are contraindicated for one medicine but not the other, and how your other medicines or health conditions interact with each option. Those questions are exactly what a prescriber works through with you. If you are already on one medicine and wondering about the other, our guide on how long after Mounjaro you can take Wegovy explains what the transition typically involves.

What happens if you stop, and the private route through nume

One finding that sits alongside SURMOUNT-5 is worth mentioning plainly: weight regain after stopping either medicine is well documented. Our page on what happens when people stop treatment covers the evidence on regain, which is why prescribers treat these as long-term medicines rather than short courses.

On the NHS, access to either medicine follows phased eligibility criteria that are still rolling out. For tirzepatide, NICE TA1026 sets the NHS threshold at a BMI of 35 or above with at least one qualifying comorbidity, within a structured weight management setting. The NHS England guidance on weight management injections explains the NHS pathway in full, including what wrap-around lifestyle support is required.

Private treatment through a regulated online pharmacy like nume is the alternative for people who meet the licensed criteria but do not yet qualify for NHS access, or who prefer not to wait. Our clinical team reviews every consultation in person, your answers go to a prescriber, not through automated scoring. If you want to understand the treatment options available, the consultation page is the place to start. Which medicine is right for you is a clinical decision our prescribers make with you, taking the full picture into account, not just a trial headline.