Mounjaro®
Starting from £179.99/mo
Start journey Learn moreWhat the trials, the licence and the clinical reality tell you
The biggest myth: 'Mounjaro and Wegovy do the same thing'
People assume these two medicines are interchangeable because both are injectable GLP-1 medicines for weight loss. They are not the same. Wegovy contains semaglutide, which activates one receptor (the GLP-1 receptor) to reduce appetite and slow how quickly food leaves the stomach. Mounjaro contains tirzepatide, the only dual-agonist weight-loss medicine licensed in the UK: it activates both the GLP-1 and GIP receptors simultaneously. That second pathway appears to produce meaningfully greater appetite suppression in many people, and the clinical-trial numbers reflect that.
In STEP 1 (68 weeks, adults with obesity and no diabetes), participants taking semaglutide 2.4mg lost an average of around 15% of their body weight, as published in the New England Journal of Medicine. In SURMOUNT-1, tirzepatide at its highest dose produced average losses of around 20–21% over 72 weeks. The gap was tested directly in SURMOUNT-5, a head-to-head open-label trial published in 2025: tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks. If you are weighing up the options and want to understand which is best, Mounjaro or Wegovy, for your situation, the answer depends on more than trial averages alone, which is where the clinical picture matters more than the headline.
If you want to see a detailed side-by-side breakdown of Wegovy and Mounjaro, we cover the trial figures and practical differences there.
What the comparison table actually looks like
A question our prescribers hear most weeks is simply: "Which one works better?" The table below sets out the key factual differences. All weight-loss figures are trial averages; individual results vary, and a prescriber assesses your full picture before recommending either.
| Mounjaro (tirzepatide) | Wegovy (semaglutide) | |
|---|---|---|
| Receptor action | Dual GIP + GLP-1 agonist | GLP-1 agonist |
| Average weight loss (pivotal trial) | ~20–21% at 15mg over 72 weeks (SURMOUNT-1, NEJM) | ~15% at 2.4mg over 68 weeks (STEP 1, NEJM) |
| UK licensed doses | 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, 15mg | 0.25mg to 2.4mg (7.2mg pen now also approved) |
| Injection frequency | Once weekly | Once weekly |
| NICE recommendation | TA1026: BMI ≥35 + ≥1 comorbidity (NHS phased rollout) | TA875: BMI ≥35 + ≥1 comorbidity, max 2 years in specialist service |
| Side-effect profile | GI-led: nausea, diarrhoea, constipation, indigestion | GI-led: nausea, diarrhoea, constipation, indigestion |
The side-effect profiles are similar for both medicines, predominantly gastrointestinal, most noticeable after starting or after a dose increase, and usually settling within a couple of weeks. Neither has a clear safety advantage over the other at this stage of their post-market experience. You can read more on the clinical differences between Wegovy and Mounjaro if you want to go deeper on the mechanism.
Eligibility, oral options and cost: the practical layer
Both medicines are licensed for adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition such as high blood pressure, type 2 diabetes or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. The NICE recommendations differ in important ways: tirzepatide (TA1026, published December 2024) does not carry the two-year cap that applies to the NHS use of Wegovy (TA875). That distinction matters mainly on the NHS; in private practice, clinical suitability guides duration regardless.
On cost, there is no simple answer, prices vary by dose and provider, and both medicines have seen significant price changes since mid-2025. A full cost comparison of Mounjaro and Wegovy sets out what the current market looks like and what a legitimate price should include. Spoiler: consultation, prescription, delivery and aftercare should all be part of whatever you pay.
It is also worth noting that Wegovy now comes in tablet form. The MHRA approved oral semaglutide for weight management in June 2026, giving people who prefer not to inject a licensed alternative. Mounjaro remains injection-only. That practical preference is a legitimate factor in a clinical discussion. And if you are curious about switching after starting one of them, switching between Wegovy and Mounjaro is not straightforward, it requires a prescriber review and a structured plan.
Ozempic comes up in this comparison regularly, too. Ozempic is also semaglutide, but it is licensed for type 2 diabetes, not weight loss, it is not a substitute for Wegovy, and comparing Mounjaro with Ozempic is a different question entirely. The NICE appraisal of tirzepatide (TA1026) and the NHS guidance on weight-management injections are the clearest official references if you want the regulatory picture in full.
Which medicine suits you is a clinical decision. Our prescribers work through your full health history, current medicines, BMI and preferences before recommending either. Check your eligibility with a free consultation and let that conversation do the work a comparison table cannot.
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