Mounjaro®
Starting from £179.99/mo
Start journey Learn moreThe facts behind the Ozempic vs tirzepatide comparison — and why the UK picture is different
The biggest misconception: Ozempic and Mounjaro are not competing weight-loss medicines
A question our prescribers hear most weeks is some version of: "Should I go on Ozempic or tirzepatide?" The comparison feels obvious, both are widely discussed, both are injections, both affect appetite. But it rests on a false premise.
Ozempic is semaglutide. In the UK, it holds an MHRA licence for type 2 diabetes management, not for weight loss. Prescribing it specifically for weight management would be off-label, and it is not the product Novo Nordisk markets for that purpose. If you are wondering whether Ozempic is a tirzepatide, the short answer is no, they are three distinct things, two of them share an active ingredient, but their licences are different.
The weight-loss-licensed semaglutide product in the UK is Wegovy (2.4mg weekly injection, with a newer 7.2mg dose now approved by the MHRA). Tirzepatide is sold as Mounjaro. These are the two medicines that belong in this comparison, and both require a prescription from a qualified prescriber who has assessed your full medical picture. The NHS page on tirzepatide and the NHS page on semaglutide explain both medicines at patient level.
How the two licensed weight-loss medicines compare
Wegovy (semaglutide) activates a single receptor (the GLP-1 pathway) to reduce appetite and slow gastric emptying. Mounjaro (tirzepatide) targets two receptors simultaneously: GLP-1 and GIP. That dual action is why tirzepatide is sometimes described as the only dual-agonist weight-loss medicine currently licensed in the UK.
In terms of average weight loss, the trial evidence favours tirzepatide. In the SURMOUNT-1 trial, people using the 15mg dose lost around 20–21% of body weight over 72 weeks. The STEP 1 trial of semaglutide 2.4mg reported roughly 15% average loss over 68 weeks. Then, in the SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, tirzepatide produced greater average weight reduction than semaglutide 2.4mg directly. The newer 7.2mg Wegovy dose reported around 20.7% average loss in its trials, narrowing that gap considerably.
The table below sets out the key comparison points. Numbers are from NICE's appraisal of tirzepatide (TA1026) and published trial data.
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist |
| Injection frequency | Once weekly | Once weekly |
| Average weight loss (standard maintenance dose, trial data) | ~20–21% at 15mg (SURMOUNT-1) | ~15% at 2.4mg (STEP 1) |
| Head-to-head evidence | Greater average loss than semaglutide 2.4mg (SURMOUNT-5, NEJM 2025) | 7.2mg dose narrows the gap (~20.7%) |
| UK weight-loss licence | Yes (BMI ≥30, or ≥27 with a weight-related condition) | Yes (same thresholds) |
| Ozempic, same active ingredient as Wegovy? | No | Yes, but Ozempic is licensed for type 2 diabetes only |
Side effects, eligibility and what the numbers cannot tell you
Both medicines share a broadly similar side-effect profile, dominated by gastrointestinal symptoms: nausea, loose stools, constipation, burping and, for some people, fatigue or headache. These effects are typically most noticeable when starting treatment or after a dose step upwards, and they often ease within a couple of weeks as the body adjusts.
Eligibility for either medicine in the UK covers adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related health condition such as high blood pressure, type 2 diabetes or obstructive sleep apnoea. Lower BMI thresholds apply for certain ethnic backgrounds under UK clinical guidance. If you are weighing up whether semaglutide or tirzepatide is the better fit for your situation, including how cost and tolerability factor in, our dedicated page walks through the evidence in detail.
What the trial averages cannot settle is which medicine is right for you. Your medical history, any other medicines you take, and how you respond to treatment all shape that answer. A prescriber, not a percentage, makes that call.
What nume dispenses for weight loss, and how to start
nume is a GPhC-registered online pharmacy (premises registration 9012878, verifiable on the GPhC register) that dispenses Mounjaro and Wegovy for weight management. Ozempic is not something we prescribe for weight loss, because it is not licensed for that purpose in the UK. If you have been reading about whether Ozempic, tirzepatide or semaglutide are the same thing, our dedicated page untangles the differences and clarifies what each product is actually approved for.
Our clinical team reviews every consultation personally. A comparison of Wegovy vs Mounjaro in more detail (including cost context and what each titration schedule looks like) may help you think through the options before you speak to a prescriber, and our guide on which is better, semaglutide or tirzepatide, covers the broader evidence in one place. You can also explore our treatment overview to see what is available.
Which of the two licensed options suits you is a clinical decision our prescribers make with you, based on your individual health picture.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.