Mounjaro®
Starting from £179.99/mo
Start journey Learn moreWhat the evidence says, and what it means for your decision right now
You've read about reta's trial results and wondered whether Mounjaro is second-best
It's a fair reaction. Phase 2 trial data for retatrutide, published in the New England Journal of Medicine, reported average weight reductions of around 24% over 48 weeks at the highest dose tested, figures that attracted considerable attention. Mounjaro's SURMOUNT-1 trial, run over 72 weeks in thousands of adults with obesity, reported average body-weight reductions of around 20–21% at 15mg, with some analyses reaching approximately 22.5%. Those numbers sit close together once you account for the different trial durations, populations and conditions. Calling reta the clear leader on the strength of a phase 2 comparison is not something the evidence currently supports.
Retatrutide works differently from tirzepatide: it activates three gut-hormone receptors (GLP-1, GIP and glucagon), whereas Mounjaro activates two (GLP-1 and GIP). Whether that third pathway translates into meaningfully better real-world outcomes (across the kind of diverse population that phase 3 trials enrol) remains an open question. Phase 3 data are still maturing. If you want to go deeper on the biology, our guide to choosing between reta or Mounjaro is a useful place to work through the decision. The full mechanistic comparison of reta and tirzepatide covers the receptor differences in more detail if you want to go deeper on the biology.
The practical point is simpler. Mounjaro is here, licensed by the MHRA, backed by phase 3 evidence and recommended by NICE in Technology Appraisal TA1026. Reta is not. For anyone weighing up their options today, that gap matters.
What the two medicines look like side by side
A head-to-head licensed comparison isn't possible yet (retatrutide has no UK licence) but a factual summary of where each stands is useful context.
| Factor | Mounjaro (tirzepatide) | Retatrutide |
|---|---|---|
| Receptor targets | GLP-1 and GIP (dual agonist) | GLP-1, GIP and glucagon (triple agonist) |
| UK licence (weight management) | Yes (MHRA authorised | No) not yet approved in the UK |
| Phase 3 trial evidence | SURMOUNT programme; ~20–21% average weight loss at 15mg over 72 weeks [NEJM, SURMOUNT-1] | Phase 3 trials ongoing; phase 2 reported ~24% over 48 weeks [NEJM] |
| NICE recommendation | Yes (TA1026, December 2024) | No appraisal yet |
| Available through UK pharmacies | Yes, via private prescription | No |
| Administration | Once-weekly subcutaneous injection (KwikPen) | Once-weekly subcutaneous injection (trial formulation) |
One quick check worth doing: visit the GPhC pharmacy register and confirm that any service you're considering is listed. It takes under a minute and tells you whether the pharmacy is regulated. If a site is offering retatrutide for sale in the UK today, that is a serious red flag; the medicine has no UK marketing authorisation and any such supply would fall outside the licensed supply chain.
For those curious about how retatrutide compares to Mounjaro across the trial data in more depth, that page goes into the specific figures and their limitations.
Who can currently access Mounjaro in the UK, and on what terms
The licensed eligibility criteria for Mounjaro cover adults with a BMI of 30 or above, or 27 and above alongside at least one weight-related condition such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. BMI alone never settles the question; the prescriber assesses the whole clinical picture.
Through the NHS, NICE TA1026 sets stricter criteria, currently BMI 40 or above with four or more of five specified conditions, with further cohorts opening through 2026 and 2027. Most people pursuing private treatment don't meet those NHS thresholds, or don't want to wait. A private prescription route through a regulated pharmacy removes the referral and the queue, subject to clinical suitability. There's a fuller breakdown of what Mounjaro is and how it works on the Mounjaro overview page if you're still building a picture of the medicine itself.
Cost is a real consideration. Eli Lilly raised UK list prices from September 2025, and private market prices for Mounjaro now typically range from around £149 to £375 per month depending on the dose and provider. The cost context page covers what those prices usually do and don't include. At nume, one price covers the consultation, the prescription, the treatment and next-working-day delivery, no add-ons. We're not the cheapest option in the market; that's a deliberate choice, not an oversight.
What to do if you want to start treatment now
Retatrutide is not available in the UK. If you've been reading about it and wondering whether Mounjaro is a reasonable alternative while you wait, yes, it is, and it has the evidence base and regulatory approval to back that up. The question of whether reta will outperform Mounjaro in licensed, real-world use remains genuinely open; phase 3 data will clarify it. Until regulatory approval arrives, comparison is largely academic.
Which medicine suits you, at what dose and alongside what lifestyle changes, is a clinical decision. Our prescribers at nume make that assessment with you, not for you. If you'd like to explore whether Mounjaro is appropriate for your situation, the free consultation is the place to start. You can also browse all of our weight-loss treatments to see the full picture before you decide. A question you don't see answered here? Our FAQs page or the team via our contact page can usually fill the gap quickly.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.