Mounjaro®
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Start journey Learn moreWhat the evidence actually shows when Mounjaro and Wegovy go head to head
What did the direct comparison trial actually find?
For a long time, comparisons between Mounjaro and Wegovy were indirect — researchers held each medicine up against placebo in separate trials and inferred a ranking. SURMOUNT-5 changed that. Published in the New England Journal of Medicine in 2025, it was a 72-week open-label trial involving 751 adults with obesity and no diabetes, randomising participants to tirzepatide or semaglutide 2.4mg. Tirzepatide produced greater average body-weight reduction. The margin was meaningful, not a rounding error.
To put numbers alongside that: SURMOUNT-1 (tirzepatide, around 2,500 participants) reported roughly 20–21% average weight reduction at the 15mg dose over the same 72-week window, per the NEJM paper. The STEP 1 trial for semaglutide 2.4mg reported approximately 15% average loss over 68 weeks. These trials used different populations and designs, so that comparison is indirect, SURMOUNT-5 is the cleaner test, and it confirmed tirzepatide's edge. NICE cited the indirect comparisons favouring tirzepatide in its appraisal, TA1026, published in December 2024.
One important nuance: Wegovy now has a 7.2mg maintenance dose approved by the MHRA (April 2026), and trial data at that higher dose reported around 20.7% average weight loss, narrowing the gap with tirzepatide considerably. If you want to explore whether Wegovy is as effective as Mounjaro given that closing gap, the comparison is more nuanced than older headlines suggest. The comparison landscape is still shifting.
Does the mechanism explain the difference in results?
Probably, yes. Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two separate gut-hormone pathways involved in appetite regulation and blood-sugar control. Wegovy is a GLP-1 receptor agonist only. Activating both pathways appears to produce a stronger appetite-suppressing effect in most people, which is the likely biological reason the trial numbers diverge.
That said, mechanism doesn't automatically mean better fit. Some people tolerate semaglutide better; others find tirzepatide's side-effect profile easier to manage. The full picture of tolerability and lifestyle fit is part of what a prescriber weighs up. GI side effects (nausea, loose stools, occasional vomiting) appear in the common-side-effects profile of both medicines, typically most noticeable after starting or after a dose increase.
If you're curious about the pharmacological detail behind the comparison, the semaglutide versus tirzepatide mechanism page goes deeper on why the dual pathway matters in practice.
How do the two medicines compare on the key practical points?
| Factor | Mounjaro (tirzepatide) | Wegovy injection (semaglutide 2.4mg / 7.2mg) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist |
| Average weight loss (headline trial figure) | ~20–21% at 15mg over 72 weeks (SURMOUNT-1, NEJM) | ~15% at 2.4mg over 68 weeks (STEP 1, NEJM); ~20.7% at 7.2mg |
| Head-to-head result | Greater average loss (SURMOUNT-5, NEJM 2025) | Lower average loss vs tirzepatide at matched doses |
| UK licence for weight management | Yes (BMI ≥30, or ≥27 with a weight-related condition | Yes) same thresholds |
| NICE recommendation | TA1026 (Dec 2024): BMI ≥35 + ≥1 comorbidity (NHS route) | TA875 (Mar 2023): BMI ≥35 + ≥1 comorbidity, specialist service, max 2 years (NHS route) |
| Format | Once-weekly subcutaneous injection (KwikPen) | Once-weekly subcutaneous injection; oral tablet (25mg) also now MHRA-approved |
Both carry a Black Triangle (▼) status, indicating additional MHRA monitoring. NICE TA875 sets out the NHS conditions under which Wegovy is recommended; Mounjaro's NHS pathway sits under TA1026.
Which one should you actually choose?
That question doesn't have a single answer, and any page that pretends otherwise is cutting corners. Trial averages describe populations, your response will depend on your medical history, any medicines you already take, your tolerance profile and what your prescriber finds in a proper assessment. Some people reach meaningful weight loss on semaglutide and have no reason to switch. Others find tirzepatide's profile suits them better from the start. It is also worth knowing that stacking semaglutide and tirzepatide together is not a safe or approved approach, so choosing between them, rather than combining them, is the right starting point.
For what it's worth, the clinical comparison page at nume lays out the eligibility criteria, NHS access routes and practical considerations side by side. Cost is part of the picture too, the Mounjaro versus Wegovy price comparison covers what UK private treatment typically costs for each, and what those figures do and don't include.
At nume, a named prescriber reviews your consultation and considers both options in the context of your health, not a ranking table. If you'd like to understand how our clinical team approaches these decisions, the answer is: carefully, with your full picture in front of them. Worth checking whether you're eligible before assuming one medicine is simply the better one.
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