Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow tirzepatide and semaglutide compare — mechanism, trial data, and UK availability
Step 1: Get the names straight, Zepbound, Mounjaro, Wegovy, Ozempic
Start with the labels, because they cause most of the confusion. Tirzepatide is the active ingredient. Eli Lilly markets it in the United States under the brand name Zepbound for weight management; in the UK, the same molecule is licensed and dispensed under the name Mounjaro. Zepbound as a brand does not appear on any UK shelf, and it cannot be obtained from a UK pharmacy. If you have seen Zepbound discussed online, you are reading about a product designed for the US market, with US pricing, US pen formats, and US regulatory approval. None of that translates directly to UK practice.
Semaglutide is a completely different active ingredient, made by Novo Nordisk. In the UK it is available as Wegovy for weight management (both the once-weekly injection and, since June 2026, a once-daily tablet) and as Ozempic for type 2 diabetes. Ozempic is not licensed for weight loss in the UK, that distinction matters clinically and legally. If you are researching whether Mounjaro and semaglutide are the same thing, the short answer is they are not: different molecules, different manufacturers, different receptor targets, and if you want a fuller breakdown of whether Mounjaro counts as a semaglutide drug, that question has its own dedicated page worth reading first.
Step 2: Understand how the two drugs actually work
Tirzepatide (Mounjaro in the UK) is a dual agonist. It activates both the GIP receptor and the GLP-1 receptor, two gut hormones involved in appetite regulation and blood-sugar control. GLP-1 receptor agonism slows gastric emptying and increases the sensation of fullness; the added GIP action appears to compound those effects, though research into the exact interplay is ongoing. It is the only dual-agonist weight-management medicine currently licensed in the UK. The NHS tirzepatide page explains the mechanism in plain language.
Semaglutide (Wegovy) is a single GLP-1 receptor agonist. It works through the same GLP-1 pathway (reducing appetite, slowing digestion, signalling fullness) but without the GIP component. Both medicines are administered as once-weekly injections in their main forms; tirzepatide comes as a six-strength KwikPen, while the Wegovy injection titrates from 0.25 mg up to either 2.4 mg or, following MHRA approval in April 2026, a 7.2 mg single-dose pen. The page on semaglutide or tirzepatide on this site explores the practical differences in more depth.
Step 3: Compare the trial evidence side by side
The table below summarises the key clinical data for each medicine. Numbers come from published trial results; individual outcomes vary and these figures should not be read as personal predictions.
| Factor | Tirzepatide (Mounjaro / US: Zepbound) | Semaglutide 2.4 mg (Wegovy injection) |
|---|---|---|
| Trial | SURMOUNT-1 (72 weeks, 2,539 adults without diabetes) | STEP 1 (68 weeks, 1,961 adults without diabetes) |
| Average weight reduction (highest dose) | ~20–21% at 15 mg [NEJM, SURMOUNT-1] | ~15% at 2.4 mg [NEJM, STEP 1] |
| Head-to-head evidence | SURMOUNT-5 (NEJM, 2025): tirzepatide produced greater average weight reduction than semaglutide 2.4 mg over 72 weeks in adults with obesity and no diabetes | |
| UK brand name | Mounjaro | Wegovy (injection or tablet) |
| US brand name | Zepbound | Ozempic / Wegovy |
| NICE recommendation | TA1026 (December 2024) | TA875 (March 2023) |
SURMOUNT-5 is the first direct head-to-head trial comparing the two medicines. Its results have been discussed in the context of Wegovy versus Mounjaro; the short version is that tirzepatide produced greater average loss, though the newer 7.2 mg Wegovy dose may narrow that gap. Neither drug is right for everyone, and a trial statistic is not a personal forecast.
Step 4: What this means for UK readers, which medicines are actually available
Zepbound cannot be prescribed or dispensed in the UK. If a seller claims to supply Zepbound to UK addresses, that is a significant red flag; the MHRA has warned repeatedly about counterfeit and unlicensed weight-loss pens sold online. The two prescription medicines licensed for weight management in the UK are Mounjaro (tirzepatide) and Wegovy (semaglutide). A useful starting point for UK weight-loss treatment options is our treatment overview, which covers both.
Eligibility for each depends on your BMI, any related health conditions, and your full medical history. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. The clinical team at nume reviews every consultation personally before any prescription is issued. There is no algorithm making that call.
If you are trying to decide between the two licensed options, the page comparing tirzepatide and semaglutide sets out the distinctions clearly. For a cost angle, the Mounjaro and Wegovy price comparison covers what private treatment typically costs by dose and provider. Which option is right for you is a clinical decision, not a shortlist exercise, our prescribers work through that with you during your consultation.
One practical note: whichever medicine is prescribed, the injection pen lives in the fridge between doses. That is worth knowing before you start, particularly if your fridge space is tight or you travel regularly.
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