Mounjaro®
Starting from £179.99/mo
Start journey Learn moreMounjaro vs Wegovy: how the evidence, mechanism and eligibility stack up
You've done the research and you're stuck between the two (here's the honest picture
A question our prescribers hear most weeks goes something like this: "I've read about both, I think I qualify for either) which one should I choose?" It is the right question to ask, and it deserves a straight answer rather than marketing copy.
Mounjaro (tirzepatide, made by Eli Lilly) works on two gut-hormone receptors (GIP and GLP-1) making it the only dual-agonist weight-loss medicine licensed in the UK. Wegovy (semaglutide, made by Novo Nordisk) targets the GLP-1 receptor alone. In practice, both slow gastric emptying, reduce appetite and help sustain a calorie deficit. The two-receptor mechanism of tirzepatide appears to produce, on average, a larger weight reduction — but the size of that difference varies by individual.
The most direct evidence comes from SURMOUNT-5, a head-to-head trial published in the New England Journal of Medicine in 2025, which found tirzepatide produced greater average weight loss than semaglutide 2.4mg over 72 weeks. Separately, NICE's appraisal of tirzepatide noted that indirect comparisons across trials favour tirzepatide at comparable doses. That said, the standard 2.4mg Wegovy maintenance dose and the newer 7.2mg option narrow the gap considerably, the dose-by-dose picture is more layered than the headline figures suggest.
The table below summarises the factual comparison. Numbers carry their source; where a range is given, it reflects variation between doses and trial designs.
| Factor | Mounjaro (tirzepatide) | Wegovy injection (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist |
| UK licence (weight management) | BMI ≥30, or ≥27 with ≥1 weight-related condition [NICE TA1026] | BMI ≥30, or ≥27 with ≥1 weight-related condition [NICE TA875] |
| Trial weight loss (headline) | ~20–21% average at 15mg over 72 weeks (SURMOUNT-1, NEJM) | ~15% average at 2.4mg over 68 weeks (STEP 1, NEJM); ~20.7% at 7.2mg |
| Dosing format | Once-weekly injection, 2.5mg–15mg; titrated by prescriber | Once-weekly injection, 0.25mg–2.4mg (or up to 7.2mg); titrated by prescriber |
| Oral option available? | No | Yes, Wegovy tablet approved by the MHRA in June 2026 |
| Contraception note | Add a non-oral method for the first 4 weeks of treatment and 4 weeks after each dose increase if using an oral contraceptive pill [NHS England] | No equivalent evidence of reduced pill effectiveness at current guidance |
What tilts the clinical decision one way or the other
Efficacy data rarely settles the question on its own. Several practical and clinical factors tend to matter just as much in a real consultation.
If you currently use the oral contraceptive pill and are not keen to add a barrier method during dose adjustments, that is worth raising with your prescriber, the absorption consideration applies specifically to tirzepatide. If you have tried semaglutide before and want to understand what a switch might involve, the clinical considerations around moving between medicines are worth reading before you consult.
For people who want to avoid injections entirely, Wegovy is now available as a daily tablet, the first oral GLP-1 medicine licensed in the UK for weight management, approved by the MHRA on 11 June 2026. That option does not exist for tirzepatide at present. Our treatment overview covers all three formats in one place.
Side-effect profiles are broadly similar across both medicines: gastrointestinal symptoms (nausea, loose stools, indigestion) are the most reported, tend to peak around dose increases, and usually settle within days to a fortnight. The January 2026 MHRA Drug Safety Update flagged acute pancreatitis as a known but infrequent risk across GLP-1 medicines, severe, persistent stomach pain that radiates to the back needs prompt medical attention with either treatment. Neither medicine is recommended during pregnancy, while breastfeeding, or when trying to conceive, and neither is licensed for under-18s.
Cost is a real consideration. Tirzepatide's UK list price rose substantially from September 2025, and private prices for either medicine vary by dose and provider. A dedicated cost comparison covers what market pricing actually looks like and what legitimate private treatment includes.
How the decision gets made, and what our prescribers look at
Neither medicine wins on every measure. Tirzepatide produces larger average weight loss in the head-to-head data. Semaglutide has a longer post-approval track record in the UK, an oral format, and no contraception interaction to manage. Some people respond better to one mechanism than the other, and individual tolerability varies.
Our prescribers look at the whole picture: your BMI, your medical history, any medicines you already take, your preferences around injection vs tablet, and your experience with weight-loss treatment if you have tried it before. If you are still weighing up the two and want a detailed walkthrough of how to choose, our guide to deciding between Wegovy and Mounjaro works through the decision factors in more detail. And if you have already been on one and are wondering about switching, what a switch from Mounjaro to Wegovy involves clinically is a different question from which to start with.
Both medicines are prescription-only. The only legal route to either in the UK is a prescription issued following a proper clinical assessment. At nume, that assessment is carried out by a GPhC-registered Independent Prescriber, the same day you complete your consultation. Which suits you is a clinical decision our prescribers make with you, start your free consultation here and bring your questions along.
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