Mounjaro®
Starting from £179.99/mo
Start journey Learn moreWhat the evidence actually tells us, and what the licensing means for your decision
The decision you're actually facing: licensed options only
Ozempic and Wegovy both contain semaglutide, made by Novo Nordisk. The difference is in how they're licensed. Ozempic is authorised in the UK for type 2 diabetes. Wegovy (the same active ingredient at a different dose) is the version licensed for weight management. Prescribing Ozempic specifically for weight loss would be off-label, and the NHS medicines guidance on semaglutide is clear about the distinction between the two brands.
Tirzepatide, sold as Mounjaro, is separately licensed for weight management in adults with a BMI of 30 or above, or 27-plus alongside a weight-related condition such as high blood pressure or raised cholesterol. So the real decision in front of most people asking this question is: Mounjaro or Wegovy? You can read a fuller breakdown of that comparison on our Wegovy vs Mounjaro page.
Neither medicine is something you simply choose from a shelf. A prescriber reviews your health history, current medicines and circumstances before any prescription is written. That clinical layer isn't an inconvenience; it's what makes the treatment safe.
How the two mechanisms differ, and why it matters for results
Wegovy (semaglutide) works on a single gut-hormone pathway: it activates GLP-1 receptors, which slow gastric emptying and reduce appetite. Mounjaro (tirzepatide) activates two pathways (GLP-1 and GIP) making it the only dual-agonist weight-loss medicine licensed in the UK. That second receptor may explain why the average weight reductions seen in tirzepatide trials sit higher than those for semaglutide at its standard 2.4mg dose.
In the SURMOUNT-1 trial, tirzepatide at its highest dose produced an average body-weight reduction of around 20-21% over 72 weeks, as published in the New England Journal of Medicine. The STEP 1 trial for semaglutide 2.4mg found an average reduction of around 15% over 68 weeks. A direct comparison came in the SURMOUNT-5 head-to-head trial (NEJM, 2025), where tirzepatide produced greater average weight loss than semaglutide 2.4mg over 72 weeks in adults without diabetes.
It's worth noting that Novo Nordisk now offers a 7.2mg semaglutide dose, approved by the MHRA in April 2026, which narrows that gap in average results. If you want to explore whether tirzepatide outperforms Wegovy across a fuller set of factors, that page goes deeper. The bottom line here: mechanism differences are real, and they translate into measurable differences in average outcomes, but averages don't predict your individual response.
A side-by-side look at the key facts
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) | Ozempic (semaglutide) |
|---|---|---|---|
| UK weight-loss licence | Yes (BMI ≥30 or ≥27 + condition) | Yes (BMI ≥30 or ≥27 + condition) | No, licensed for type 2 diabetes only |
| Receptor mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist | GLP-1 agonist |
| Average trial weight loss | ~20-21% at highest dose (SURMOUNT-1, NEJM) | ~15% at 2.4mg (STEP 1, NEJM); ~20.7% at 7.2mg | Not applicable for weight loss |
| Administration | Once-weekly injection (KwikPen) | Once-weekly injection | Once-weekly injection |
| NICE recommended for weight loss on NHS | Yes, under TA1026 | Yes, under TA875 (specialist services) | No |
One quick check worth doing: if you've found a clinic or website offering Ozempic for weight loss, spend 30 seconds searching its name on the GPhC pharmacy register. A GPhC-registered pharmacy will always confirm which medicines it holds a licence to dispense and for what indication, and that verification takes under a minute.
What this means if you're deciding which medicine to pursue
Ozempic isn't a route to weight management treatment in the UK, at least not through any legitimate, on-label pathway. If someone's offering it to you for weight loss, that's a flag worth thinking carefully about. The licensed options (Mounjaro and Wegovy) have both been through rigorous UK regulatory review, and NICE has published recommendations for both: TA1026 for tirzepatide and TA875 for semaglutide.
Which of the two is right for you depends on your BMI, medical history, any medicines you already take, and how your body responds to treatment. People switching from Ozempic to a licensed weight-loss medicine sometimes find the transition straightforward, but it still needs clinical oversight, our switching from Ozempic to tirzepatide page covers what that process typically involves.
Common side effects for both medicines are led by gastrointestinal symptoms: nausea, loose stools, constipation and indigestion are the ones most people encounter, usually in the early weeks. Both carry the same Black Triangle status with the MHRA, meaning they're under additional monitoring as relatively new medicines. If you're weighing up the two and want to know whether tirzepatide is better than Ozempic across the factors that actually matter clinically, that page works through the evidence in detail. For a fuller look at how the two approved weight-loss options sit against each other in the UK context, the Ozempic vs Mounjaro comparison page goes through the nuances in more detail.
The honest close: no comparison table settles this. A prescriber who knows your picture does. Check your eligibility and explore your options through our free consultation, a real clinician reads every submission the same day.
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