How Much Weight Will You Lose on Tirzepatide?

What do the trial results actually show?

SURMOUNT-1 randomised 2,539 adults with obesity but without type 2 diabetes. At 15mg (the maximum licensed dose) participants lost an average of around 20–21% of body weight over 72 weeks alongside a reduced-calorie diet and increased activity. Some analyses put the figure at up to 22.5%. For context, that's roughly 20–22 kg shed by someone starting at 100 kg.

The head-to-head picture sharpened further with the SURMOUNT-5 trial, published in 2025, which compared tirzepatide directly with semaglutide 2.4mg in adults with obesity. Tirzepatide produced greater average weight loss over 72 weeks. A fuller breakdown of what those percentages mean at different starting weights can help put the numbers in context.

These are averages. About a third of participants in SURMOUNT-1 lost 25% or more; some lost less than 10%. If you want to understand how much weight you might lose on Mounjaro, it helps to look at what the trial data suggests for people with a similar starting point to you. The right expectation is meaningful, clinically significant weight loss. A specific number isn't something any clinician can guarantee.

Does the dose you reach change how much you lose?

Yes, substantially. Results at lower doses such as 5mg are noticeably smaller than at 10mg or 15mg. Treatment starts at 2.5mg — the first pen's job is letting your system adjust, not producing weight loss. Titration then follows roughly every four weeks, guided by your prescriber.

Not everyone reaches 15mg. Some people do very well at 10mg; others need to pause titration because of side effects. Your prescriber makes that call based on how you're tolerating the medicine and how your weight is progressing. There's useful guidance on what progress looks like at each stage, worth reading before your consultation if you want to set realistic expectations.

NICE's appraisal of tirzepatide, TA1026, notes that if someone hasn't lost at least 5% of body weight after six months at the highest tolerated dose, continuing treatment should be reviewed. That's a real benchmark, not a scare, just the clinical test the evidence supports.

What does tirzepatide cost in the UK, and what should that include?

UK private pricing for tirzepatide varies by provider and dose. Since Eli Lilly raised the medicine's UK list price from September 2025 (the highest dose's list price rose from around £122 to around £330 per four-week pen) typical private market prices have ranged roughly £149–£375 per month depending on dose and supplier, as widely reported.

That range is where the comparison gets complicated. Some headline prices cover the medicine only. Consultation fees, prescription charges, delivery costs and any aftercare support may be listed separately, added at checkout, or simply absent. A quick check worth doing before you commit: read the provider's pricing page in full, then ask what happens if you need clinical advice between doses. If the answer isn't clear, that tells you something.

At nume, one price covers the consultation, the prescription, the medicine, tracked next-working-day delivery and seven-day aftercare. We're not the cheapest option in this market, that's a deliberate choice. A full breakdown of how tirzepatide pricing works in the UK gives more context on what to compare beyond the headline number. Current treatment pricing is shown on our treatment page.

Why is 'cheapest' the wrong question for a prescription medicine?

Tirzepatide sold without a clinical assessment, via social media or unverified websites, is a serious safety risk. The MHRA has warned repeatedly about counterfeit weight-loss pens, fake pens seized in enforcement operations have been found to contain insulin, and there have been hospitalisations. In October 2025, the first illicit UK site producing counterfeit tirzepatide pens was raided in Northampton; across 2025, around 20 million doses of illegally traded weight-loss medicines (roughly £45m street value) were seized. Report suspected sellers at the MHRA Yellow Card site.

Price is the wrong test for a medicine that only works safely when it's genuine, correctly stored and clinically supervised. The questions that matter: Is the pharmacy on the GPhC register? Does a real prescriber review your case? Is the medicine coming through the licensed UK supply chain? How nume works answers each of those directly. You can verify any online pharmacy at the GPhC register, our premises number is 9012878.

If the weight-loss results from tirzepatide are what drew you here, getting the medicine from a verified, clinically supervised source is what makes those results achievable. Find out more about Mounjaro (the UK brand name for tirzepatide), or check your eligibility with our prescribers today.