Are Wegovy and Mounjaro the Same Medicine?

The core difference: one receptor versus two

Wegovy (semaglutide, made by Novo Nordisk) acts on a single receptor, the GLP-1 receptor, which is involved in appetite signalling and slowing how quickly the stomach empties. Mounjaro (tirzepatide, made by Eli Lilly) activates both the GLP-1 receptor and a second receptor, GIP, making it the only dual-agonist weight-loss medicine currently licensed in the UK. Whether that second pathway translates into a meaningfully different experience for any given individual is something a prescriber works through with you, it is not a foregone conclusion. What the clinical evidence does show is that the two medicines produce different average outcomes at their highest licensed doses, which is worth understanding before you start. If you want a detailed walk-through of the mechanism comparison, the does Wegovy work the same as Mounjaro page covers it fully. The Ozempic and tirzepatide comparison is also worth a read if you have seen those names used interchangeably, and if you are also asking whether Wegovy and Mounjaro are essentially the same treatment, the short answer is no, they differ in meaningful ways that are laid out there.

Both medicines are given by once-weekly subcutaneous injection and both are Black Triangle medicines, meaning the MHRA collects additional monitoring data on them. Starting doses for both are intentionally modest, the first weeks are about tolerability, not weight loss.

What the trial evidence actually shows

The clearest comparison comes from the SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025. In a 72-week head-to-head study of adults with obesity and no diabetes, tirzepatide produced a greater average weight reduction than semaglutide 2.4mg. That finding was also noted in the NICE committee discussion for tirzepatide (NICE technology appraisal TA1026). For context: SURMOUNT-1 reported an average body-weight reduction of around 20–21% at the 15mg tirzepatide dose over 72 weeks, while STEP 1 reported approximately 15% average reduction with semaglutide 2.4mg over 68 weeks. These are population averages from clinical trials, not individual predictions, your result will depend on your starting point, your dose, and how you respond. It is also worth noting that Novo Nordisk has since received MHRA approval for a higher 7.2mg semaglutide maintenance dose, which narrows the gap in trial data to some degree.

The table below sets out the key factual differences side by side.

Eligibility, side effects and what they share

The licensed eligibility criteria are almost identical. Both medicines are approved for adults with a BMI of 30 or above, or a BMI of 27 to 29.9 alongside at least one weight-related condition such as high blood pressure, raised cholesterol or type 2 diabetes. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. The NHS England weight-management injections guidance sets out the clinical detail for both.

The side-effect profiles overlap considerably too. Nausea, constipation, diarrhoea and indigestion are common with both, especially when starting or after a dose increase, and typically settle over a few weeks. Neither medicine is recommended during pregnancy, breastfeeding or for anyone under 18. One practical difference: if you take an oral contraceptive pill, NHS guidance advises adding a non-oral method for the first four weeks of tirzepatide and for four weeks after each dose increase, because tirzepatide may reduce pill absorption. That specific caution does not currently apply to semaglutide in the same way. It takes under a minute to check the current patient leaflet for your medicine on the electronic medicines compendium (eMC), a habit worth building whenever your dose changes.

For a closer look at how the two medicines compare on cost, the Mounjaro versus Wegovy cost comparison page has current context. And if you are wondering whether switching makes sense after trying one, the will Wegovy work if Mounjaro didn't page addresses that question directly.

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

Choosing between these two medicines is a clinical decision, not a rankings exercise. A prescriber considers your BMI, your existing health conditions, other medicines you take (including contraception and HRT), your preferences around injection frequency and device, and your previous experience of either treatment. The average trial figures point in a direction, but averages describe populations, they do not determine individual outcomes.

At nume, a real clinician reviews every consultation the same day it is submitted. There is no algorithm assigning treatments; your prescriber reads your answers and makes a judgement. The broader comparison of Wegovy versus Mounjaro across multiple factors is covered on the Wegovy vs Mounjaro page, and if you want to read about our clinical team's approach, the clinical team profile has more detail. Both medicines are available as private prescriptions through our GPhC-registered pharmacy (registration number 9012878, verifiable at the GPhC register), subject to clinical suitability. Speak to our prescribers through a free consultation, the conversation starts there.