Wegovy vs Mounjaro for Weight Loss: What the Evidence Shows

Step 1: Understand what each medicine actually does

Mounjaro works by activating two receptors simultaneously: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1. This dual action slows gastric emptying, reduces appetite and influences energy regulation through two separate pathways. It is the only licensed weight-loss medicine in the UK with this dual mechanism. You can read the clinical background on the NHS tirzepatide medicine page.

Wegovy acts on GLP-1 alone, the same receptor targeted by older GLP-1 medicines, but at a higher dose than was previously used for diabetes. That single-pathway approach has a long track record and a substantial body of trial evidence behind it. Wegovy also holds a cardiovascular risk-reduction licence in the UK, which is relevant for some patients with heart disease; Mounjaro's cardiovascular trial programme is ongoing. For readers comparing semaglutide across its different uses, our page on semaglutide versus Mounjaro for weight loss covers the full picture.

Neither is the same as Ozempic. Ozempic contains semaglutide at lower doses and is licensed for type 2 diabetes, not weight management, and anyone switching from Mounjaro to Ozempic for weight loss should understand that this would be an off-label use, and it is not what either NICE appraisal recommends. That distinction matters when you see online listings that blur the two.

Step 2: Look at the results evidence side by side

The table below pulls the published trial figures for each medicine. These are averages from well-controlled studies; individual results vary.

The SURMOUNT-5 trial is the first direct head-to-head comparison. It is worth reading the NICE appraisal of tirzepatide (TA1026) and NICE's appraisal of semaglutide (TA875) if you want to understand how the committee weighed the evidence. Neither document is bedtime reading, but both are public and freely accessible.

The Wegovy 7.2mg approval is genuinely significant. When the MHRA cleared the new single-dose 7.2mg pen in April 2026, the average trial result at that dose brought semaglutide's ceiling much closer to tirzepatide's. The gap between them is narrowing. That is useful context for anyone who was told a year ago that Wegovy was clearly weaker. For a more detailed comparison of the two medicines across every angle our readers ask about, see Mounjaro versus Wegovy for weight loss.

Step 3: Consider side effects and practical differences

The side-effect profiles of both medicines are broadly similar because both influence gastric emptying: nausea, loose stools, constipation, indigestion and fatigue are the most commonly reported effects, usually at their worst after starting or after a dose increase, and generally easing within a week or two for most people. The NHS semaglutide page and the equivalent tirzepatide page both list what to watch for.

There are some practical differences worth knowing. Mounjaro comes as a KwikPen delivering four weekly injections from one pen; Wegovy uses a separate pen for each weekly injection. Both require refrigerated storage. Neither has a fridge-to-pocket window you should guess at, the exact timeframes are in the Patient Information Leaflet, and we refer every patient there. If you are ever away over a bank holiday or payday timing means you want to order ahead, the leaflet's storage guidance is the only number that counts.

One specific clinical note on contraception: women using oral contraceptive pills who start tirzepatide should use an additional barrier method for the first four weeks of treatment and for four weeks after each dose increase, because the pill's absorption may be reduced. NHS guidance does not flag the same concern for semaglutide. If you are on the pill, this is worth raising at consultation.

For a closer look at how people switch between these medicines in practice, the page on the clinical differences between Mounjaro and Wegovy goes into the details our prescribers discuss most often.

Step 4: Think about access, eligibility and what the consultation resolves

Both medicines are prescription-only. Neither can be legally supplied without a clinical assessment, regardless of where you look online. For private treatment, the licensed eligibility criteria for both medicines start at a BMI of 30, or 27 with at least one weight-related condition such as high blood pressure, high cholesterol, type 2 diabetes or sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. BMI is a starting point, not the whole picture, the prescriber considers your full health history.

On the NHS, Mounjaro is now available through primary care for people who meet the NICE TA1026 criteria, though GP practice participation varies and the rollout is phased by comorbidity count and BMI. Wegovy on the NHS remains routed through specialist weight management services under TA875, with commonly long waiting lists. Private treatment through a regulated online pharmacy bypasses those waiting lists, subject to clinical suitability.

At nume, a named prescriber reviews every consultation personally on the day it arrives, not a triage algorithm. If you are eligible for either medicine, they will discuss which is the better fit for your situation, and our detailed guide on Mounjaro vs Ozempic can help you arrive at that conversation better informed. The question of which is clinically better for weight loss is one our prescribers work through with each patient individually. You can also browse an overview of our available treatments on the weight loss treatments page before starting. Which medicine suits you is a clinical decision our prescribers make with you, not one a comparison table can settle.

Check your eligibility by starting your free consultation today.