Mounjaro®
Starting from £179.99/mo
Start journey Learn moreWhat the trial evidence says, and what it means for your own expectations
The numbers the clinical trials actually produced
The two largest modern trials give us the clearest picture available. In SURMOUNT-1, published in the New England Journal of Medicine, adults taking tirzepatide (Mounjaro) at its highest dose lost around 20 to 21% of their body weight on average over 72 weeks, with some analyses reaching closer to 22.5%. That trial randomised 2,539 participants, so the figures carry genuine statistical weight. In STEP 1, semaglutide 2.4mg (Wegovy) produced an average reduction of around 15% over 68 weeks in adults with obesity. Both medicines were taken alongside a reduced-calorie diet and increased activity, that pairing matters, because neither medicine operates independently of how you eat and move.
A direct head-to-head comparison came from the SURMOUNT-5 trial, published in 2025, which found tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks. Wegovy's newer 7.2mg dose, approved by the MHRA in early 2026, is narrowing that gap, with trials reporting around 20.7% average loss at that maintenance dose. The honest summary: how much weight you lose on injections depends substantially on which medicine you are prescribed and at what dose, and that is a clinical decision, not a consumer one.
If you want to understand how individual results compare across medicines, our treatment overview page sets out the licensed options side by side.
Why 'how much weight will I lose?' is the right question but harder to answer than it looks
Reading a percentage from a trial is straightforward. Translating it into your own life is less so, and that gap is worth being honest about. Trial participants follow tightly controlled protocols; in real-world use, people miss doses, stop and restart, adjust their titration pace, and bring far more varied medical histories. NHS England's guidance on weight management injections notes that medicines work best alongside sustained behavioural support, not because willpower is the variable, but because appetite reduction from a GLP-1 or dual-agonist medicine is most productive when protein intake, hydration and activity are actively maintained.
Many people reading this are probably weighing up whether the results are real, whether the price is justified, and whether they will be one of the people for whom this works well. Those are fair questions. The clinical evidence is genuinely strong (stronger than for any previous weight management medicines) but individual results remain individual. What a prescriber can do, which a headline percentage cannot, is look at your specific situation: your BMI, your health history, any medicines you already take, and which treatment is most likely to suit you.
Our clinical team's approach to that assessment is described on our about page, and you can read more about the prescribers involved at our clinical team profile.
What weight loss injections typically cost in the UK, and what the price actually includes
Private weight loss injection treatment in the UK is priced per pen or per month, and it varies by medicine, dose and provider. Since Eli Lilly raised Mounjaro's UK list price from 1 September 2025, typical private prices across the market have ranged roughly £149 to £375 per month depending on dose and provider, as widely reported. Those figures are market context, not a quote from any specific pharmacy.
What headline prices often leave out is worth understanding before you compare. Some providers charge separately for the initial consultation, the repeat prescription, delivery, and any clinical support if you have a question or a side effect. Those add-ons can shift the real monthly cost considerably. If you are wondering how much is the weight loss injection you have been prescribed specifically, that page walks through pricing by medicine and dose. A fuller breakdown of how much weight loss injections are likely to cost you across different treatment plans is worth reading before you commit to any provider. If you want to compare what different dose points typically cost, our guide on how much weight loss injections are covers that in more detail, and for a structured breakdown of the figures, our page on how much weight loss injections cost sets out the numbers by medicine and dose. If you are also trying to get a clearer sense of what you would pay before starting, our page on how much it is for weight loss injections breaks that down in straightforward terms.
At nume, one price covers the consultation, the prescription, the treatment itself, and free next-working-day delivery. We are not the cheapest option in the market, and that is a deliberate choice rather than an oversight. The reason is straightforward: clinical review, identity and weight verification, genuine supply-chain sourcing, and seven-day aftercare cost something. Cutting those is how providers get the price down, and cutting those is also where the risk enters.
Why 'cheapest' is not the measure that protects you here
For most purchases, price is a perfectly sensible filter. For a prescription medicine (one that requires titration, monitoring, and clinical oversight) it is the wrong test. The MHRA has warned publicly about counterfeit weight loss pens sold online, some of which have contained insulin rather than the stated active ingredient, resulting in serious harm. In 2025 alone, approximately 20 million doses of illegally traded weight loss medicines (with a street value of around £45 million) were seized, and the first illicit UK manufacturing site producing fake tirzepatide pens was raided. The MHRA's Yellow Card reporting site allows anyone to report a suspect seller.
The safe route for any of these medicines is a prescription following a genuine clinical assessment, dispensed by a pharmacy you can verify on the GPhC register. Red flags include sellers offering these treatments without a prescription, prices far below market rate, and discount codes from unverified sources. A small saving measured in pounds is not the measure that matters when the medicine going into your body could be counterfeit. If you have questions about what legitimate treatment involves, our FAQs cover the most common ones, or you can get in touch directly.
If you are ready to find out whether you are clinically suitable, the right next step is a free consultation, reviewed the same day by a real prescriber, with no obligation to proceed.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.