What's stronger than semaglutide — and does it matter for you?

You're looking at two medicines and wondering which one actually works harder

That's a reasonable thing to want to know. The short answer is that tirzepatide (sold in the UK as Mounjaro) produces greater average weight loss than semaglutide 2.4mg in clinical trials, and the science behind that difference is fairly clear. Semaglutide mimics one gut hormone, GLP-1, which slows gastric emptying and reduces appetite. Tirzepatide does the same, and also activates a second receptor, GIP, which appears to amplify those effects. Two pathways rather than one.

The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, put this directly to the test: 751 adults with obesity but without diabetes, randomly assigned to tirzepatide or semaglutide 2.4mg for 72 weeks. Tirzepatide produced meaningfully greater average weight reduction. That's the most robust comparison we have, because it was a direct head-to-head, not an estimate drawn from separate trials with different populations. You can read more about how semaglutide works as a weight-loss medicine to put those results in context.

A common misconception is that a higher dose of semaglutide would simply match or beat tirzepatide at its ceiling. The 7.2mg semaglutide dose (approved by the MHRA in early 2026 and discussed further on our page about the stronger Wegovy approval) does narrow the gap, reporting around 20.7% average weight loss over 72 weeks. That's closer to tirzepatide 15mg territory. But closer isn't equal, and the prescriber's job is to assess which medicine fits the person in front of them, not just to reach for the highest number.

What the SURMOUNT-5 results mean in practice

Trial percentages deserve a little unpacking. When SURMOUNT-5 reports that tirzepatide outperformed semaglutide 2.4mg, those are group averages across hundreds of participants, some people on semaglutide lost more weight than some people on tirzepatide, and vice versa. Biology varies. What the data tells us is that, at a population level, the dual-agonist approach produces a larger effect. For any individual, results depend on starting weight, adherence, lifestyle, dose tolerance and a cluster of factors that no trial can fully predict.

SURMOUNT-1, tirzepatide's landmark phase-3 trial, reported average body-weight reductions of around 20–21% at the 15mg dose over 72 weeks, in thousands of adults with obesity. Wegovy at 2.4mg showed around 15% average reduction in the STEP 1 trial. Neither figure is a promise; both figures are cited by NICE in their respective appraisals. If you're weighing up the evidence for yourself, the comparison between semaglutide products is another useful reference point, because the licensed doses and indications differ.

On cost, there's a practical dimension worth knowing. Tirzepatide at higher doses carries a higher list price, Eli Lilly raised Mounjaro's UK list price significantly from September 2025, with the highest-dose pen now around £330 per four-week supply at list. Private prices across providers typically range from roughly £149 to £375 per month depending on dose. You can see how those figures break down on our guide to treatment costs. Price alone is a poor guide to suitability; the two medicines aren't interchangeable by cost.

Where the newer semaglutide dose fits, and what's still on the horizon

The MHRA's April 2026 approval of a dedicated 7.2mg semaglutide pen changed the conversation slightly. Semaglutide is no longer a fixed-ceiling medicine at 2.4mg; its ceiling has moved. That matters because some patients do better on semaglutide from a tolerability standpoint, and a higher dose may now get them further. The approval is specifically for adults with a BMI of 30 or above (it doesn't extend to the cardiovascular-risk indication at that dose) and the titration still starts at 0.25mg, with a prescriber managing each step. Details on the highest licensed semaglutide dose explain this more fully.

Beyond these two medicines, retatrutide (a triple-agonist targeting GIP, GLP-1 and glucagon receptors simultaneously) is generating significant trial interest. Early-phase data suggest it may outperform both semaglutide and tirzepatide. It is not yet licensed in the UK, so it remains a research story rather than a clinical option for now. There's a separate page on retatrutide versus semaglutide if you want to follow that pipeline.

The NICE appraisal of tirzepatide (TA1026) and NICE's recommendation for semaglutide (TA875) both provide the clinical evidence framework that UK prescribers work within. Neither medicine is automatically the right one. A prescriber at a regulated service weighs your BMI, comorbidities, medication history and personal circumstances, that's what clinical assessment is for.

Which is right for you, and how the decision gets made

Potency rankings are useful background. They're not a prescription. A medicine that's technically stronger on average in trials can still be the wrong choice for a specific person: if tirzepatide interacts with another medicine you take, or if your blood-pressure history raises a flag, the prescriber will factor that in. The same applies in reverse, semaglutide at 2.4mg or 7.2mg may be entirely appropriate where tirzepatide isn't.

The NHS guidance on tirzepatide and the NICE appraisal TA1026 are the authoritative UK references if you want to read the clinical rationale. What they won't do is tell you which medicine you should be on, that requires a conversation with a prescriber who can see your full picture. If you'd like ours to review yours, you can start a free consultation with our clinical team and get an answer the same day.