Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow the mechanisms, results and eligibility compare side by side
Picture this: you've been told both names and you're not sure which question to ask first
You've probably read fragments, a headline about Mounjaro producing bigger weight loss, a friend who's been on Wegovy for a year, maybe a TikTok that mentioned "the GLP-1 jab" without distinguishing between them. It's a reasonable place to feel confused, because from the outside they look almost identical: one injection a week, both licensed for weight management in UK adults, both made by major pharmaceutical companies. If you want a clear breakdown of the difference between Mounjaro and Wegovy, that covers the core distinctions before we get into the detail below.
Wegovy is semaglutide, made by Novo Nordisk. It mimics a gut hormone called GLP-1, which slows the speed at which food leaves the stomach, reduces appetite signals and helps regulate blood sugar. The STEP 1 trial, published in the New England Journal of Medicine, found an average body-weight reduction of around 15% over 68 weeks at the 2.4mg maintenance dose.
Mounjaro is tirzepatide, made by Eli Lilly. It activates both GLP-1 and a second receptor, GIP, making it the only dual-agonist weight-loss medicine licensed in the UK. That second pathway appears to add to the appetite and metabolic effects. In the SURMOUNT-1 trial, average weight reduction at the 15mg dose reached around 20–21% over 72 weeks. Then there's the head-to-head evidence: in the SURMOUNT-5 trial, referenced in NICE's appraisal of tirzepatide (TA1026), tirzepatide produced greater average weight reduction than semaglutide 2.4mg in adults with obesity who did not have type 2 diabetes. Worth knowing.
These are population averages from controlled trials. Your individual response depends on your health picture, which medicines you've tried before and how your body responds to treatment. That's exactly the kind of assessment a prescriber works through with you.
Side-effect profiles: similar territory, worth understanding the detail
Both medicines share a gastrointestinal side-effect profile. Nausea is the most commonly reported complaint, followed by vomiting, diarrhoea, constipation, indigestion and fatigue. For most people these are strongest at the start of treatment or after a dose increase, and they tend to ease within a couple of weeks as the body adjusts. You can read a full breakdown on the NHS's tirzepatide medicine page and the equivalent semaglutide page.
One difference worth flagging: women taking oral contraceptives alongside tirzepatide are advised to use an additional non-oral method, such as condoms, for the first four weeks of treatment and for four weeks after each dose increase, because Mounjaro may reduce pill absorption. NHS guidance does not flag the same concern for semaglutide. If you're on the pill, that's a detail your prescriber will discuss with you, and if you're considering switching between the two medicines, it's worth raising at that point specifically.
The MHRA issued a Drug Safety Update in January 2026 highlighting acute pancreatitis as an infrequent but potentially serious side effect across the GLP-1 class. Severe stomach pain radiating to the back, with or without vomiting, warrants urgent medical attention. Both medicines carry a Black Triangle (▼) symbol, meaning they're under additional MHRA monitoring while post-market data continues to build.
Eligibility in the UK: private and NHS routes differ for each
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Private licence (adults) | BMI ≥30, or ≥27 with a weight-related condition | BMI ≥30, or ≥27 with a weight-related condition |
| How often | Once weekly (subcutaneous injection) | Once weekly (subcutaneous injection) |
| NICE recommendation | TA1026: BMI ≥35 + ≥1 comorbidity (NHS route) | TA875: BMI ≥35, specialist service, max 2 years (NHS route) |
| Average weight loss (trials) | ~20–21% at 15mg (SURMOUNT-1, 72 weeks) | ~15% at 2.4mg (STEP 1, 68 weeks) |
| Higher dose option | Up to 15mg | Up to 7.2mg (single-dose pen, MHRA approved April 2026) |
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist |
For both medicines, BMI thresholds under UK guidance are 2.5 kg/m² lower for people from South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds. A lower number on paper does not mean automatic approval, the prescriber considers your full health picture regardless of which route applies.
If you're curious about the cost difference between Mounjaro and Wegovy, that varies by dose and provider; our treatment page shows current pricing. A few people also ask about Ozempic versus Mounjaro, Ozempic is also semaglutide, but it is licensed for type 2 diabetes in the UK, not weight management, so it belongs in a different conversation entirely.
Which one is right for you? That's the clinical question
There is no universal answer, and nobody should give you one without knowing your medical history. Some people are better candidates for one over the other based on existing conditions, other medicines they take, tolerance to injections or their prescriber's clinical judgement. The trial evidence suggests tirzepatide produces greater average weight loss, but the question isn't which medicine wins a comparison table, it's which is appropriate for you specifically.
Our prescribers look at this as part of your free consultation. You can also explore the Wegovy vs Mounjaro overview for a broader look at the two, or read more about the key practical differences if you want to go deeper before speaking to a clinician. For anything about our clinical team's approach, meet our lead prescriber.
If you've done your reading and you're ready to take the next step, check your eligibility, it takes a few minutes, costs nothing, and a named prescriber reads your answers the same day.
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