Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow the three medicines compare on evidence, mechanism and UK licensing
What the clinical trials found for each medicine
The clearest picture comes from the head-to-head data. In the STEP 1 trial published in the New England Journal of Medicine, semaglutide 2.4mg (Wegovy) produced an average body-weight reduction of around 15% over 68 weeks in adults with obesity and no diabetes. That was a significant advance on liraglutide 3mg (Saxenda), which in earlier SCALE trials produced roughly 5–8% average weight loss over a similar period. The gap is substantial enough that NICE's clinical guidance now reflects the newer agents as the preferred pharmacological options.
Tirzepatide (Mounjaro) has since shifted the picture further. In SURMOUNT-1, involving 2,539 adults with obesity, average weight loss reached around 20–21% at the 15mg dose over 72 weeks. Then came SURMOUNT-5, a direct head-to-head published in the New England Journal of Medicine in 2025: tirzepatide produced greater average weight reduction than semaglutide 2.4mg across 72 weeks in adults with obesity and no diabetes. NICE's appraisal of tirzepatide (TA1026) reflects this, and the committee discussion notes that indirect comparisons favour tirzepatide over semaglutide for weight loss.
Saxenda's trial results remain valid, but the scale of difference means it now occupies a different clinical conversation than it did five years ago.
How the mechanisms differ, and why Saxenda is not dispensed by nume for weight loss
All three work on appetite regulation, but the pathways are not identical. Saxenda and Wegovy are both GLP-1 receptor agonists: they mimic the gut hormone GLP-1, slowing gastric emptying and increasing the feeling of fullness after eating. Saxenda uses liraglutide and is injected daily; Wegovy uses semaglutide and is injected once weekly. Mounjaro adds a second mechanism, it activates both the GIP and GLP-1 receptors, making it the only dual-agonist weight-loss medicine currently licensed in the UK.
Saxenda is licensed in the UK for weight management. However, nume does not dispense Saxenda. The medicines available through our prescribers for weight loss are Mounjaro and Wegovy, both of which hold current MHRA authorisation for weight management and have the stronger evidence base for meaningful weight reduction. If you have been told about Saxenda elsewhere and are wondering whether it is still the right choice, that is exactly the kind of question a prescriber can work through with you. You can explore both licensed options on our weight-loss treatments page.
Side by side: key facts for Mounjaro, Wegovy and Saxenda
| Feature | Mounjaro (tirzepatide) | Wegovy (semaglutide) | Saxenda (liraglutide) |
|---|---|---|---|
| Injection frequency | Once weekly | Once weekly | Once daily |
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist | GLP-1 agonist |
| Average weight loss (pivotal trial) | ~20–21% at 15mg (SURMOUNT-1, NEJM) | ~15% at 2.4mg (STEP 1, NEJM) | ~5–8% at 3mg (SCALE trials) |
| UK-licensed for weight management | Yes | Yes | Yes |
| Available through nume | Yes | Yes | No |
| NICE-recommended for weight management | Yes (TA1026, Dec 2024) | Yes (TA875, Mar 2023) | No NICE TA for weight management |
Sources: NICE TA1026 (tirzepatide); NICE TA875 (semaglutide); NEJM SURMOUNT-1; NEJM STEP 1.
Mounjaro versus Wegovy: the practical comparison that matters most
For most people researching these medicines today, the real comparison is between Mounjaro and Wegovy. Both are once-weekly injections. Both are GPhC-dispensable on private prescription. The trial data consistently show a larger average reduction with tirzepatide, though individual response varies and the prescriber's assessment of your health history, current medicines and weight-related conditions matters as much as any trial average. People switching between the two do so for various reasons, tolerability, dose availability, a change in clinical priority. Our detailed Wegovy versus Mounjaro comparison covers the nuances, and if you are already on one and wondering about the other, the considerations involved in moving from Mounjaro to Wegovy are worth reading before you ask your prescriber.
One practical note: pricing differences between the two are real and worth understanding before you assume they reflect a quality difference, they largely reflect separate manufacturer pricing decisions. A prescriber does not choose between them on cost; they choose on clinical fit. If you want to explore how the two medicines sit alongside each other from a different angle, our pages looking at Mounjaro va Wegovy and Wegovy v Mounjaro each approach the comparison from a slightly different starting point and may answer questions this page has not. If your situation is more specific, perhaps you are already taking one and weighing up a change, the guidance on moving from Mounjaro to Wegovy sets out what that transition typically involves.
Whichever medicine this page has helped you think about, the next step is the same. A consultation with one of our prescribers (reviewed the same day, with identity and weight verified, and your medical history read properly) is how that clinical decision gets made with you, not for you. Which medicine suits you is not a question a comparison page can answer. It is a clinical decision our prescribers make with you. You can start your free consultation when you are ready, or read more about our approach on the about us page.
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