Mounjaro®
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Start journey Learn moreTirzepatide versus semaglutide: the factors that shape this clinical decision
The core difference: one receptor versus two
This is a question our prescribers hear most weeks, and it is a good one. The confusion is understandable: Mounjaro and Wegovy look similar on the surface. Both are once-weekly subcutaneous injections. Both are licensed in the UK for weight management alongside a reduced-calorie diet and increased physical activity. Both slow gastric emptying and reduce appetite. Yet the pharmacology is meaningfully different.
Semaglutide, the active ingredient in Wegovy, targets a single gut hormone receptor: the GLP-1 receptor. Tirzepatide, the active ingredient in Mounjaro, targets two receptors simultaneously, GLP-1 and GIP. It is the only dual-agonist weight-loss medicine currently licensed in the UK. Whether activating that second pathway produces a clinically relevant difference for any individual patient is something the evidence addresses, and something a prescriber weighs alongside your personal health picture. You can read more about how these medicines differ at a biochemical level on our page exploring whether Mounjaro is semaglutide.
The NHS medicines pages for tirzepatide and for semaglutide explain the mechanism clearly if you want a regulator-approved plain-English description alongside what follows here.
What the trial evidence shows, and what it does not decide for you
In SURMOUNT-1, a 72-week phase 3 trial involving 2,539 adults with obesity, tirzepatide at the highest dose produced an average body-weight reduction of around 20 to 21 percent. In the STEP 1 trial, semaglutide 2.4mg produced an average reduction of around 15 percent over 68 weeks. Those figures come from different trials, different populations and different durations, so a direct numerical comparison carries real limitations.
The more informative evidence is the SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, which compared tirzepatide directly with semaglutide 2.4mg over 72 weeks in adults with obesity and no diabetes. Tirzepatide produced greater average weight loss. NICE's appraisal of tirzepatide (TA1026) also notes that indirect comparisons favour tirzepatide over semaglutide at the doses studied. The gap narrows with Wegovy's newer 7.2mg dose, for which trials reported around 20.7 percent average loss, approaching tirzepatide 15mg territory. A fuller side-by-side breakdown, including the SURMOUNT-5 data, is available on our Wegovy versus Mounjaro comparison page.
None of that decides which medicine works better for you. Trial averages describe populations; prescribers assess individuals.
Comparing the two medicines: a factual snapshot
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Active ingredient | Tirzepatide | Semaglutide |
| Receptor targets | GLP-1 and GIP (dual) | GLP-1 only |
| UK weight-loss licence | Yes (BMI ≥30, or ≥27 with comorbidity) | Yes (BMI ≥30, or ≥27 with comorbidity) |
| Average weight loss (trial) | ~20–21% at 15mg (SURMOUNT-1, NEJM) | ~15% at 2.4mg (STEP 1, NEJM); ~20.7% at 7.2mg |
| Administration | Once-weekly injection, KwikPen | Once-weekly injection, pre-filled pen |
| Oral option available? | No | Yes, Wegovy tablets (approved June 2026) |
A note on Ozempic: it contains semaglutide but is licensed for type 2 diabetes management, not weight loss. It is not a weight-management treatment, and prescribers should not prescribe it for that purpose. If you have seen references to Ozempic in a weight-loss context, our page on whether Ozempic contains tirzepatide addresses that confusion directly.
Which medicine belongs in your conversation with a prescriber?
The practical decision comes down to your medical history, current medicines, BMI, and any weight-related conditions you have. Both tirzepatide and semaglutide are prescription-only medicines under UK law. A prescriber reviews your full clinical picture before recommending either, there is no shortcut to that step, and there should not be.
Contraception matters here too: if you take an oral contraceptive pill, tirzepatide can temporarily reduce its absorption during the first four weeks of treatment and for four weeks after each dose increase, so an additional non-oral method is advised during those windows. NHS guidance does not flag the same issue for semaglutide. That is one concrete clinical reason the choice of medicine is not simply about which produced a bigger trial average.
Cost context is another factor many people weigh. The price difference between Mounjaro and Wegovy is real and worth understanding before you decide. At nume, one transparent price covers your consultation, prescription, treatment and next-day delivery, no subscriptions, no hidden fees. For a prescription medicine, price is not the metric that matters most, but transparency around it does.
If you want to explore the options with a prescriber, check your eligibility and our clinical team will review your consultation the same day. You can also read more about whether semaglutide and Mounjaro are the same thing, or compare the two medicines in more depth on our Wegovy vs Mounjaro page. Which suits you is a clinical decision our prescribers make with you.
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