Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow the evidence compares — and what it means for your choice
What do the trial results actually show about Mounjaro vs Wegovy?
Mounjaro belongs to a newer class of medicine: it activates both the GIP and GLP-1 receptors, the two main gut-hormone pathways involved in appetite and blood-sugar regulation. Wegovy targets the GLP-1 receptor only. That dual mechanism is the reason the weight-loss numbers diverge.
In SURMOUNT-1 (2,539 adults, 72 weeks), participants on Mounjaro 15 mg lost an average of around 20–21% of body weight. The STEP 1 trial for Wegovy 2.4 mg (68 weeks) showed roughly 15% average loss. Those figures come from separate studies with different participant populations, so they are not a clean apples-to-apples comparison, a point worth examining in more detail.
SURMOUNT-5 addressed that limitation directly. In this open-label, 72-week head-to-head trial of 751 adults with obesity and without diabetes, tirzepatide produced statistically greater weight reduction than semaglutide 2.4 mg. NICE's appraisal of tirzepatide (TA1026) noted that indirect and direct comparisons both favour tirzepatide, and that shaped its recommendation. That said, Wegovy's newer 7.2 mg dose (approved by the MHRA in January 2026 and available as a dedicated single-dose pen from April 2026) showed around 20.7% average loss in trials, narrowing the gap considerably.
So is Mounjaro more effective? On average, across the trials, yes. But averages describe populations, not individuals.
| Mounjaro (tirzepatide) | Wegovy (semaglutide) | |
|---|---|---|
| Receptor target | GIP + GLP-1 (dual agonist) | GLP-1 only |
| Average weight loss in trials | ~20–21% at 15 mg (SURMOUNT-1, 72 wks) [NEJM] | ~15% at 2.4 mg (STEP 1, 68 wks); ~20.7% at 7.2 mg [NEJM] |
| Head-to-head trial | SURMOUNT-5 (NEJM 2025): tirzepatide produced greater average loss than semaglutide 2.4 mg at 72 weeks | |
| UK licence (weight) | BMI ≥30, or ≥27 with a weight-related condition | BMI ≥30, or ≥27 with a weight-related condition |
| Delivery | Once-weekly injection (KwikPen) | Once-weekly injection; or once-daily tablet (25 mg maintenance) |
| NICE recommendation | TA1026 (Dec 2024, updated Sep 2025) | TA875 (Mar 2023) |
Does a bigger trial number mean Mounjaro is the right choice for you?
There's a misconception that floats around: that the medicine with the highest headline percentage is automatically the better pick for everyone. It doesn't work that way. How well either medicine suits you depends on your health history, any other medicines you take, whether you prefer an injection or a tablet, how your body responds to a GLP-1 or dual-agonist mechanism, and a range of other factors a prescriber weighs up.
Wegovy also comes in tablet form. The oral Wegovy tablet (approved by the MHRA on 11 June 2026, the first oral GLP-1 weight-loss medicine licensed in the UK) reaches a 25 mg daily maintenance dose and showed roughly 13.6% average weight loss in the OASIS 4 trial (and around 17% among participants who stayed fully adherent). For someone who is needle-averse or travels frequently, that distinction can matter far more than a percentage-point difference in averages.
Side effects also feed into the decision. Both medicines carry a GI-led side-effect profile (nausea, loose stools, indigestion and similar complaints are the most commonly reported) but individual tolerance varies. Safety considerations across both medicines are worth reviewing before any decision is made. The prescriber's job is to match medicine to person, not to chase the number at the top of the comparison table.
What do NICE and UK clinical guidance say about choosing between them?
NICE has appraised both medicines. Tirzepatide (TA1026) is recommended for adults with a BMI of 35 or above and at least one weight-related comorbidity; thresholds are 2.5 kg/m² lower for South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds. Semaglutide (TA875) is recommended for use within specialist weight management services, for a maximum of two years, under similar BMI criteria.
Private prescribing follows the licensed eligibility criteria set out in each medicine's SmPC rather than the NHS commissioning criteria, which means the BMI and comorbidity thresholds that apply through a private service like ours can differ from those the NHS currently funds. Cost also differs between the two, and it is a legitimate factor in a long-term treatment plan.
Our prescribers review both options with you during the consultation. The clinical team considers everything: your starting point, your health background, your preference for how treatment is delivered, and how your body has responded to anything similar before. The Wegovy-versus-Mounjaro question has a different answer for different people, and that's exactly what the consultation is designed to work out. You can read about our clinical team and how we approach prescribing decisions.
If you're also curious how either compares with other medicines, our broader comparison page covers additional options. And if you've seen Ozempic mentioned in the same breath as these two, it's licensed for type 2 diabetes (not weight management) which our Mounjaro vs Ozempic page explains clearly.
Ready to talk through which option suits your situation? Start your free consultation and a prescriber will review your answers the same day.
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