Mounjaro and Wegovy: are they the same thing?

You've heard both names and you're not sure if they're the same medicine under two brands

That confusion is completely understandable. Both injections are weekly, both are pre-filled pens, both are licensed for weight management in adults in the UK, and both produce significant weight loss in clinical trials. From the outside they can look almost identical. The difference lies inside the pen.

Mounjaro contains tirzepatide, made by Eli Lilly. Tirzepatide activates two gut-hormone receptors simultaneously (GIP and GLP-1) which is why it is sometimes described as a dual agonist. No other weight-loss injection licensed in the UK does this. Wegovy contains semaglutide, made by Novo Nordisk. Semaglutide targets one receptor, GLP-1, and is described as a GLP-1 receptor agonist. Both slow gastric emptying and reduce appetite, but the dual-pathway approach of tirzepatide appears to produce a stronger overall effect in most people who have been studied.

If you want to read further about how tirzepatide and semaglutide relate more broadly, the Mounjaro and semaglutide comparison on this site covers the pharmacology in more depth. Similarly, there is a longer look at whether tirzepatide and Wegovy are the same if you want to work from the ingredient names rather than the brand names.

What the trial numbers actually show when you put them side by side

The simplest way to hold the evidence in mind is to look at what each medicine achieved in its main phase-3 trial against placebo, and then what happened when they were tested directly against each other.

Those average-loss figures come from participants at the highest doses studied. Individual results vary considerably, and no trial figure is a personal prediction. The SURMOUNT-5 head-to-head is the strongest direct evidence available; NICE's appraisal of tirzepatide also noted that indirect comparisons favour tirzepatide. The arrival of the higher-dose Wegovy 7.2mg pen narrows that gap somewhat (trials reported around 20.7% average loss at 7.2mg over 72 weeks) so the picture continues to evolve.

For a more granular side-by-side, the Wegovy vs Mounjaro comparison page goes into the dose schedules, side-effect profiles and eligibility criteria in detail.

Where they are the same, and a habit worth building before you choose

The shared ground is meaningful. Both medicines are prescription-only, injected subcutaneously once a week, and stored in the fridge. Both carry a Black Triangle (▼) in the UK, meaning the MHRA collects extra safety data on them. Both have a similar side-effect profile led by gastrointestinal symptoms: nausea, loose stools, constipation, indigestion and fatigue are the most commonly reported, and they tend to be most noticeable in the early weeks or after a dose increase. Both require a prescriber's review before any dose change.

One habit worth building before you pick up either pen: check that the pharmacy you are considering appears on the GPhC pharmacy register. It takes under a minute. If a seller is not listed there, walk away, counterfeit pens have been seized in large quantities by the MHRA, and some have contained entirely different substances.

Both Mounjaro and Wegovy are sourced through the licensed UK supply chain at nume. You can read more about who we are and how our pharmacy operates, or check our FAQs for common questions about the process.

Eligibility and what the prescriber considers when choosing between them

The licensed eligibility for both overlaps: 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. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. But meeting those numbers is the start of the conversation, not the end.

A prescriber weighing up Mounjaro versus Wegovy for a specific person looks at more than the trial averages. Medical history, current medicines, whether the patient has tried one already, cardiovascular conditions, and personal preference (including whether a needle-free oral option might be relevant) all come into the discussion. The cost difference matters too, an honest breakdown of what each costs in private practice, and what that price includes, is on the Wegovy and Mounjaro cost comparison page.

Neither medicine is suitable during pregnancy, while breastfeeding, or for anyone trying to conceive. Neither is licensed for people under 18. These are not edge cases; they are conditions the prescriber checks at every stage.

The bottom line: are Wegovy and Mounjaro the same thing? No. They share a category and a delivery method, but they are different medicines at a molecular level and produce different average outcomes in the evidence. If you are still weighing up the two and wondering whether Wegovy is the same as Mounjaro, our dedicated page works through that question in full before you speak to a prescriber. Which is the better fit for you is a clinical decision our prescribers make with you, based on your full picture. If you are ready to start that conversation, check your eligibility with a free consultation.