Mounjaro®
Starting from £179.99/mo
Start journey Learn moreWhat the evidence actually shows, and why the licence matters
The misconception: that Ozempic and Mounjaro are rival weight-loss options
It is easy to see why people ask this question. Both medicines involve weekly injections. Both contain compounds that act on GLP-1 receptors. Both have been widely covered in the press alongside dramatic weight-loss figures. The assumption that follows (that they are simply two different brands competing in the same lane) is understandable, but it is wrong.
Ozempic contains semaglutide at doses of 0.5mg, 1mg and 2mg, and the MHRA has authorised it for adults with type 2 diabetes. It was never submitted for a UK weight-management licence; that authorisation belongs to Wegovy, which also contains semaglutide but at a higher 2.4mg maintenance dose (now up to 7.2mg) specifically studied for obesity. You can read more about the distinction between the two semaglutide brands on our Ozempic and Mounjaro comparison page.
Mounjaro (tirzepatide) works differently again. It activates both GLP-1 and GIP receptors (two separate gut-hormone pathways involved in appetite and blood-sugar regulation) making it the only dual-agonist weight-loss medicine currently licensed in the UK. That mechanistic difference is not just marketing; it partly explains the divergence in trial results. If you want a closer look at how Ozempic and Mounjaro relate to each other, we cover the key distinctions in detail. If you are weighing up the two licensed options side by side, our Wegovy vs Mounjaro page covers that ground in detail.
What the trial data says, and what it cannot tell you about yourself
Because Ozempic was studied in people with type 2 diabetes rather than in obesity trials, its weight-loss numbers come from a different context than Mounjaro's SURMOUNT programme or Wegovy's STEP programme. Comparing them directly is not straightforward.
What we do have is a genuine head-to-head. The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, randomised adults with obesity (without diabetes) to tirzepatide or semaglutide 2.4mg (Wegovy, not Ozempic) over 72 weeks. Tirzepatide produced greater average weight reduction. The STEP 1 trial of semaglutide 2.4mg reported around 15% average body-weight reduction over 68 weeks; SURMOUNT-1 reported around 20–21% at the 15mg tirzepatide dose. SURMOUNT-1 is published in the NEJM for anyone who wants the primary data.
None of those figures are promises. Trial participants follow controlled protocols. Individual response varies considerably depending on starting weight, adherence, diet, activity and biology. A number that applies to a study population tells you something useful about a medicine's potential; it does not tell you what will happen to you specifically. That is what a clinical assessment is for. If you are trying to decide between the two, our page looking at whether Wegovy is just as good as Mounjaro sets out what the evidence actually shows. You can explore how the two licensed weight-loss medicines compare more fully on the Wegovy and Mounjaro comparison page.
| Medicine | Active ingredient | UK weight-loss licence? | Mechanism | Average weight loss (landmark trial) |
|---|---|---|---|---|
| Ozempic | Semaglutide 0.5–2mg | No, type 2 diabetes only | GLP-1 receptor agonist | Not applicable for weight-loss indication |
| Wegovy (injection) | Semaglutide up to 2.4mg (up to 7.2mg) | Yes (NICE TA875) | GLP-1 receptor agonist | ~15% at 2.4mg over 68 weeks (STEP 1, NEJM) |
| Mounjaro | Tirzepatide 2.5–15mg | Yes (NICE TA1026) | Dual GIP and GLP-1 receptor agonist | ~20–21% at 15mg over 72 weeks (SURMOUNT-1, NEJM) |
Sources: NICE technology appraisal TA1026 (tirzepatide); NICE technology appraisal TA875 (semaglutide); NEJM trial publications.
The medicines that are actually licensed, and how to access them
If you are looking for a clinically supervised weight-loss medicine in the UK, the two options with a proper weight-management licence are Mounjaro and Wegovy. Both are prescription-only medicines. A prescriber considers your BMI, your health history, any other medicines you take, and your personal circumstances before deciding which, if either, is appropriate.
For Mounjaro, NICE recommends it for adults with a BMI of 35 or above plus at least one weight-related condition, with lower BMI thresholds applying for some ethnic backgrounds under UK guidance. Private eligibility via a licensed pharmacy may differ; the prescriber makes that call individually. For Wegovy, NICE recommends it within a specialist weight-management service context, also for adults with at least one weight-related comorbidity. The differences in how semaglutide and tirzepatide work at the molecular level are sometimes relevant to that conversation.
At nume, our prescribers review consultations personally. We prescribe Mounjaro and Wegovy; Ozempic is not something we dispense for weight loss, because it is not licensed for it. The right starting point is a consultation, not a comparison chart. You can explore the treatment options we offer on the weight-loss treatments overview, and our clinical team page introduces the prescribers behind the service. Which medicine suits you (if one does at all) is a clinical decision our prescribers make with you.
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