Is Retatrutide Better Than Mounjaro for Weight Loss?

Step 1: Understand what retatrutide actually is

Retatrutide is a triple-hormone receptor agonist being developed by Eli Lilly. Where Mounjaro activates two gut-hormone pathways (GIP and GLP-1), retatrutide also targets the glucagon receptor, making it a so-called triagonist. The theory is that engaging a third pathway produces additional energy expenditure beyond what a dual agonist achieves. Early phase-2 trial results, published in 2023, reported average weight loss of around 24% over 48 weeks at the highest doses, figures that drew significant attention.

Those numbers are genuinely striking. They are also from a relatively small, shorter-duration study, without the head-to-head comparison against active competitors that regulators require before licensing. Phase-3 trials are underway, but as of summer 2026 retatrutide has not received marketing authorisation from the MHRA, the FDA, or any other major regulator. It is not available through any UK pharmacy, licensed or otherwise. Anyone offering it online is not selling an authorised medicine.

The full retatrutide versus Mounjaro picture is worth reading alongside this page if you want more detail on the mechanism differences.

Step 2: See what Mounjaro has actually demonstrated, in licensed use

Mounjaro has completed a large clinical programme. The SURMOUNT-1 trial (2,539 adults with obesity, 72 weeks) showed average body-weight reduction of around 20–21% at the 15mg dose, with some analyses reaching approximately 22.5%. That evidence base underpins its UK licence for weight management, granted by the MHRA, and NICE's recommendation (TA1026) for adults with a BMI of 35 or above plus at least one weight-related condition. You can read NICE's full appraisal of tirzepatide (TA1026) for the committee's assessment of the evidence.

Mounjaro also outperformed semaglutide 2.4mg in the SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025. That's the kind of direct comparison regulators and clinicians actually use to understand where a medicine sits. Retatrutide has no equivalent comparison yet. If you're curious whether any current option is genuinely better than Mounjaro, that comparison covers the licensed alternatives in detail.

Pricing context matters too, Mounjaro costs in the UK have shifted since Eli Lilly raised its list price in September 2025, and understanding what a legitimate prescription includes is part of making a sensible decision.

Step 3: Compare like for like

A clean comparison is only fair where data exists on both sides. The table below reflects what is currently known.

Phase-2 figures and phase-3 figures from a fully licensed programme are not directly comparable. Sample sizes, trial length and design all affect the numbers. If you want a closer look at whether retatrutide is actually better than Mounjaro, that page works through the evidence on both sides in detail. People who are also wondering whether a GLP-1 medicine is better than Mounjaro will find a detailed breakdown of how the receptor pathways compare and what the evidence currently supports. The NHS medicines page for tirzepatide on NHS.uk sets out what is known about Mounjaro based on the licensed evidence base, which is a useful grounding for any conversation with a prescriber.

Step 4: What to do if you're weighing up your options now

If retatrutide gains a UK licence in the future, the picture may change. For now, the practical question is which licensed medicine suits your circumstances, and that's not something a comparison article can answer. It depends on your health history, any existing conditions, what medicines you already take, and what a prescriber finds after reviewing your full picture. Some people find the idea of a daily tablet more appealing than a weekly injection; others want the longest evidence record available. Those are real considerations worth raising.

People sometimes ask us about this kind of thing right after payday, or on a Monday morning when they've decided they finally want to do something about their weight. Curiosity about newer options is completely understandable, it's just worth knowing that 'promising trial results' and 'available now' are two very different things.

The Mounjaro treatment page covers eligibility, how the process works and what's included at nume. For a broader look at what licensed treatments exist, the weight-loss treatment overview is a good starting point. Our clinical team reviews every consultation personally, a prescriber decides what's right for you, not a protocol. Which medicine suits you is a clinical decision our prescribers make with you. Start your free consultation when you're ready.