Mounjaro®
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Start journey Learn moreWhat the evidence actually says, and where the comparison gets more nuanced
The biggest misconception: that one medicine is universally 'stronger' than the other
The most common framing online is that tirzepatide beats semaglutide, full stop. The trial data do broadly support tirzepatide producing larger average reductions, but that reading glosses over something worth understanding. SURMOUNT-5 compared tirzepatide at its highest tolerated dose against semaglutide at 2.4mg, and tirzepatide came out ahead on average body-weight reduction over 72 weeks. What that result cannot tell you is how you specifically will respond. Individual variation in these medicines is real and clinically meaningful. Some people lose considerably more weight on semaglutide than others lose on tirzepatide, because body chemistry, tolerability and adherence all matter alongside the headline dose comparison, and whether tirzepatide is actually better than semaglutide depends on far more than a single trial average.
There is also the question of what happens at higher semaglutide doses. The MHRA approved a 7.2mg semaglutide pen in April 2026, with trials reporting around 20.7% average weight loss over 72 weeks, a figure that narrows the gap with tirzepatide 15mg meaningfully. Our detailed comparison of tirzepatide and semaglutide covers this in full, including what the head-to-head evidence does and does not tell us. The short version: the difference is real, but less absolute than the simple ranking implies.
Both medicines are licensed in the UK for weight management in adults, and both carry a Black Triangle (▼) denoting additional MHRA monitoring. Neither is a diabetes drug repurposed informally, that applies to Ozempic and Rybelsus, which contain semaglutide but are licensed for type 2 diabetes, not weight loss, and are not the same thing as Wegovy.
How the two medicines differ mechanistically, and why it might matter
Tirzepatide (Mounjaro) acts on two gut-hormone receptors: GIP and GLP-1. Semaglutide (Wegovy) targets only GLP-1. That dual action is the reason researchers expected tirzepatide to outperform on average, and the SURMOUNT-1 trial (involving 2,539 adults with obesity) reported average weight reductions of around 20–21% at the 15mg dose over 72 weeks, as published in the NEJM. STEP 1, the equivalent semaglutide trial, reported around 15% at 2.4mg.
In practice, the mechanistic difference translates to measurable but not dramatic real-world divergence for most people. Both slow gastric emptying, reduce appetite and produce similar GI side-effect profiles, nausea, constipation, indigestion and fatigue are common to both, particularly when starting or after a dose increase, and tend to settle as the body adjusts. The oral semaglutide tablet (Wegovy tablets, approved by the MHRA in June 2026) introduces another variable: some people simply prefer not to inject, and that preference has a genuine bearing on adherence and therefore on outcomes.
If you are curious how the two medicines compare on tolerability as well as results, this page weighs up tirzepatide against Wegovy specifically from a practical perspective. The question of whether semaglutide suits certain people better is also worth reading before drawing conclusions.
Side-by-side: the key facts at a glance
| Factor | Tirzepatide (Mounjaro) | Semaglutide (Wegovy injection) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist |
| Average weight loss in pivotal trial | ~20–21% at 15mg over 72 weeks (SURMOUNT-1) | ~15% at 2.4mg over 68 weeks (STEP 1) |
| Head-to-head result | Greater average loss vs semaglutide 2.4mg (SURMOUNT-5, NEJM 2025) | Gap narrows at 7.2mg dose (MHRA approved April 2026) |
| UK licence for weight management | Yes (Mounjaro; BMI ≥30 or ≥27 with a weight-related condition) | Yes (Wegovy; same thresholds) |
| Formulation | Once-weekly injection (KwikPen) | Once-weekly injection; once-daily tablet (Wegovy tablets, approved June 2026) |
| NICE recommendation | TA1026 (December 2024, updated September 2025) | TA875 (March 2023; max 2 years, specialist service) |
Sources: NICE TA1026; NICE TA875; NEJM SURMOUNT-1 and STEP 1 trial publications.
What this means when you are actually choosing
On average weight loss over 72 weeks, tirzepatide has the stronger evidence base today. That is a fair statement. It is not the same as saying it will work better for you specifically, or that semaglutide is the wrong choice. A prescriber weighs your medical history, any existing conditions, which other medicines you take, your tolerance of injections versus tablets, and your goals, none of which a trial average can capture.
Cost sometimes enters the conversation here too. Eli Lilly raised Mounjaro's UK list price significantly from September 2025, and private market prices by dose and provider now typically sit in the £149–£375 per month range across both medicines. A breakdown of how the two medicines compare on cost is worth reading if that is part of your thinking. People who have already started one medicine and are wondering about switching (or who have moved from Mounjaro to Wegovy and noticed more hunger) can find relevant detail on what to expect after switching.
At nume, every comparison like this one ends the same way: a named prescriber reads your consultation and makes the recommendation with you. If you are ready to take that step, check your eligibility and start your free consultation. If you want to read more first, our clinical team page explains who reviews your case.
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