GLP-1 vs Mounjaro: how does tirzepatide compare to other GLP-1 medicines?

What actually separates a dual-agonist from a standard GLP-1?

GLP-1 receptor agonists mimic the gut hormone GLP-1, which slows gastric emptying, reduces appetite and helps regulate blood sugar. Medicines like semaglutide (Wegovy) work on this single pathway. If you want a detailed breakdown of how these two approaches compare, our page on GLP-1 versus Mounjaro sets out the differences clearly. Tirzepatide, sold in the UK as Mounjaro, adds a second: GIP, or glucose-dependent insulinotropic polypeptide. GIP plays a distinct role in fat storage and energy balance, and the two signals together appear to produce a stronger appetite-suppressing effect than either alone.

The NICE appraisal of tirzepatide (TA1026) summarised indirect comparisons noting that tirzepatide produces greater average weight loss than semaglutide 2.4mg. That conclusion was later reinforced by a direct head-to-head trial. In SURMOUNT-5 (published in the New England Journal of Medicine in 2025) adults with obesity randomised to tirzepatide lost more weight on average over 72 weeks than those on semaglutide 2.4mg. Neither trial enrolled children; both medicines are licensed for adults only.

The gap is meaningful but not absolute. Wegovy's 7.2mg dose, approved by the MHRA in early 2026, narrows it: trials at that dose reported around 20.7% average weight loss over 72 weeks. Whether the difference matters for a particular person depends on their starting weight, their comorbidities and how their body responds, which is precisely the kind of question a prescriber is there to answer. You can explore that question further on our page covering whether a standard GLP-1 might suit you better than Mounjaro.

How do the licensed indications actually differ across these medicines?

Mounjaro is licensed in the UK for weight management in adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition such as high blood pressure, high cholesterol or type 2 diabetes. It is also licensed for type 2 diabetes. Wegovy (semaglutide 2.4mg weekly injection) carries the same weight-management indication, along with a separate licence to reduce major cardiovascular event risk in eligible adults, and a conditional approval from July 2026 for a form of fatty liver disease (MASH).

Ozempic is also semaglutide, but it is licensed for type 2 diabetes, not weight loss. Prescribing it for weight management is off-label, and the NHS is clear that Ozempic is a diabetes medicine. If you have seen it mentioned in the context of weight loss, it is worth understanding that the licensed route is Wegovy, not Ozempic. Similarly, Rybelsus (oral semaglutide at 3, 7 or 14mg) is licensed for type 2 diabetes; it is not the same as the Wegovy tablet approved for weight loss in June 2026.

Saxenda (liraglutide) is a GLP-1 medicine licensed for weight management in the UK, but the trial data show smaller average weight reductions than either tirzepatide or semaglutide 2.4mg, and nume does not dispense it. Pages comparing GLP-1 medicines to tirzepatide more broadly cover those distinctions in more depth.

Do the side-effect profiles differ between Mounjaro and GLP-1 medicines?

The side-effect profile of Mounjaro and GLP-1 medicines like Wegovy overlaps considerably. Nausea, loose stools, constipation, indigestion and fatigue are common across the class, particularly after starting or following a dose increase, and tend to settle within a week or two for most people. Injection-site reactions occur with any subcutaneous injection.

In January 2026, the MHRA highlighted acute pancreatitis as a known but uncommon risk across GLP-1 medicines. Seek urgent medical help for severe stomach pain that radiates to the back, with or without vomiting, and report any suspected side effects at the MHRA's Yellow Card service. There is no evidence that the dual-agonist mechanism of tirzepatide meaningfully changes this risk profile compared to semaglutide, though direct comparison data remain limited.

One practical note for anyone on oral contraceptives: tirzepatide slows gastric emptying enough to reduce pill absorption in the early weeks of treatment and after each dose increase. Adding a barrier method during those periods is the standard advice. The same concern has not been documented for semaglutide. If you are considering switching between these medicines, our prescribers cover exactly this kind of transition, the considerations around switching from a GLP-1 to tirzepatide are worth reading before you decide.

Is there a version of this question that a prescriber should settle for you?

Most people searching this comparison are trying to decide between Mounjaro and Wegovy, or wondering whether the newer 7.2mg Wegovy dose changes the calculation. The honest answer is that the numbers favour tirzepatide on average weight loss (the SURMOUNT-5 head-to-head confirms it) but averages hide individual variation. A person who tolerates semaglutide well and has been stable on it for a year is not the same case as someone starting fresh.

Cost is part of this too. Since Eli Lilly adjusted its UK list price in September 2025, private Mounjaro prices have typically ranged from around £149 to £375 per month depending on dose and provider, as widely reported. Both medicines sit in a similar bracket at lower doses; the gap widens at the top. At nume, one price covers everything (consultation, prescription, delivery and aftercare) and you can see current treatment prices on our weight-loss treatments page. We are not the cheapest option in the market, by design; what that buys you is a same-day clinical review, a GPhC-registered pharmacy dispensing from the licensed supply chain, and prescribers who are available seven days a week.

There are also newer agents on the horizon. Retatrutide, a triple-agonist, has generated significant trial interest, our comparison of retatrutide and Mounjaro covers where that research currently stands. Nothing in that class is licensed in the UK for weight management yet. For now, Mounjaro and Wegovy are the two evidence-backed, licensed, dispensable choices. Which one fits your clinical picture is a decision our prescribers make with you, not one a comparison table can make for you.