Medicines Like Mounjaro: What They Have in Common and Where They Differ

The biggest myth: that these medicines are all basically the same

It's easy to assume that medicines described as "like Mounjaro" are simply cheaper or earlier versions of the same thing. They're not. The active ingredients differ, the receptor targets differ, and the clinical trial evidence differs in meaningful ways. Mounjaro contains tirzepatide, which activates both the GIP and GLP-1 receptors involved in appetite regulation and blood-sugar control. Every other weight-loss medicine in this category activates GLP-1 only. If you've been wondering whether tirzepatide is like Mounjaro and how closely the two are related, that page unpacks the relationship in full. That biological difference is why you'll find the two medicines discussed separately on the tirzepatide overview and why the trial results aren't directly interchangeable.

Wegovy, the main alternative licensed for weight management in the UK, contains semaglutide. It's a well-studied medicine, the STEP 1 trial, published in the New England Journal of Medicine, found around 15% average body-weight reduction over 68 weeks at the 2.4mg maintenance dose. Mounjaro's SURMOUNT-1 results were higher (roughly 20–21% at 15mg), and the head-to-head SURMOUNT-5 trial confirmed tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks. These are population averages from controlled trials; individual responses vary, and the right medicine for you is a clinical question, not a ranking exercise.

One more thing worth correcting early: Ozempic is also semaglutide, but it's licensed for type 2 diabetes. Searching for it as a weight-loss option leads people in the wrong direction. The NHS is clear on this distinction, and any regulated prescriber will be too.

The UK-licensed options that genuinely compare to Mounjaro

In practical terms, adults in the UK who are eligible for a weight-management medicine have three licensed options at present. Mounjaro (tirzepatide) as a once-weekly injection. Wegovy (semaglutide) as a once-weekly injection, now available up to a 7.2mg maintenance dose following MHRA approval in early 2026. And Wegovy tablets (oral semaglutide) approved by the MHRA on 11 June 2026 as the first oral GLP-1 medicine licensed for weight management in the UK. If you'd like to read more about weight-loss tablets that compare to Mounjaro, that page covers the oral option in detail.

The licensed eligibility criteria for all three require adults to have a BMI of 30 or above, or 27 or above alongside 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. BMI alone doesn't determine approval, a prescriber reviews the full clinical picture, including other medicines you take and your health history.

Each medicine titrates gradually upward. Mounjaro starts at 2.5mg (a dose designed to let your system adjust, not a therapeutic target), rising in steps prescribed by your clinician. Wegovy injection follows a similar step-up pattern. The Wegovy tablet begins at 1.5mg daily and works up to a 25mg maintenance dose. The NHS medicines page on tirzepatide is a reliable place to read about how Mounjaro works at a patient level.

Side effects: similar family, not identical profile

Because these medicines share the GLP-1 mechanism, their side-effect profiles overlap substantially. Nausea is the most commonly reported, particularly when starting or after a dose increase. Diarrhoea, constipation, indigestion, fatigue and headache also appear across all three. For most people these settle within days to a couple of weeks; that's part of why titration is gradual.

There are differences in detail. The contraception interaction is one worth knowing: for tirzepatide specifically, women taking oral contraceptives are advised to use an additional non-oral method for the first four weeks of treatment and for four weeks after each dose increase, because absorption of the pill may be reduced. NHS guidance does not apply the same caution to semaglutide. It's a small but real practical difference, and one a prescriber will raise at assessment. If you're curious about how Mounjaro actually feels day-to-day, the page on what Mounjaro feels like covers patient experience in honest terms.

On cost context: the price of these medicines has shifted over the past year. Eli Lilly raised Mounjaro's UK list price from September 2025, with the highest dose rising from around £122 to around £330 per four-week pen. Typical private prices since then range roughly £149–£375 per month by dose and provider. You can read more about what that price increase means in practice, and there's a broader look at weight-loss treatment options if you're still working out which direction makes sense.

What a prescriber actually considers when choosing between them

A clinician weighing up Mounjaro versus a semaglutide-based option will look at several things: your BMI and current weight-related conditions, any medicines you already take, whether you'd prefer a daily tablet or a once-weekly injection, and your history with GI conditions. Trial evidence can inform that conversation, but it doesn't replace it. The SURMOUNT-5 head-to-head result is genuinely useful information; it doesn't mean tirzepatide is objectively correct for everyone.

There's also the practical question of timing and continuity. Some people contact us mid-month because their current supply has run out, or right after payday when they've finally decided to start. The conversation with a prescriber is the same whenever you have it. At nume, every consultation is reviewed the same day by a real clinician on our team, not a decision tree. If you'd like to understand how that process works before committing to anything, our Mounjaro page covers the full picture, or you can read about all the weight-loss treatments we offer.

These are prescription-only medicines. The best next step, if you're considering any of them, is a clinical conversation rather than a comparison table. Speak to our prescribers to find out whether you're eligible and which option fits your circumstances.