Retatrutide: frequently asked questions

Retatrutide is Eli Lilly's triple GLP-1/GIP/glucagon receptor agonist, currently in phase 3 clinical trials. It is reporting the strongest weight-loss results of any drug in its class so far, but it is not licensed or available anywhere in the world yet.

Yes. "Reta" is simply the shorter, informal name people use for retatrutide — you'll see it in trial discussion, forums and search the same way "semaglutide" gets shortened to "sema." It's not a different drug or a different formulation, just a nickname. Occasional alternative spellings you might encounter searching — "retratrutide," "retarutide," "retatrudide," "retitutide" — all refer to the same compound.

It activates three hormone receptors at once — GLP-1 and GIP (which most other GLP-1 medicines also target) plus glucagon, which raises resting energy use and increases fat breakdown in the liver. That third pathway is the leading explanation for its larger trial results.

Semaglutide (Wegovy, Ozempic) targets one receptor. Tirzepatide (Mounjaro's active ingredient) targets two. Retatrutide targets three. Each additional receptor has, so far, corresponded to stronger trial results — semaglutide around 15%, tirzepatide around 20–22%, retatrutide up to 30.3%.

No. Retatrutide is a peptide hormone-receptor agonist — it works on GLP-1, GIP and glucagon receptors, the same class of mechanism as semaglutide and tirzepatide. It has no relationship to anabolic steroids or corticosteroids, and doesn't work by the same biological pathway at all.

No. It is not licensed anywhere in the world. The only lawful way to receive it in the UK today is as a participant in an authorised clinical trial.

Eli Lilly plans to submit a US FDA application in the first quarter of 2027. FDA review typically takes 10–12 months, so US approval is realistic for late 2027 to 2028. UK approval through the MHRA would likely follow, probably late 2027 to mid-2028 at the earliest, with NHS access through NICE appraisal likely later still.

No. It is not licensed anywhere in the world, and the MHRA has explicitly warned that products sold in the UK claiming to contain retatrutide are likely illegal and potentially dangerous. The MHRA has raided three separate UK sites manufacturing or distributing unlicensed retatrutide since October 2025, most recently in May 2026.

No, not yet, anywhere — a common misconception. Retatrutide is still in phase 3 trials in the US too. Eli Lilly plans to file its FDA application in the first quarter of 2027; approval, if granted, would realistically land in late 2027 or 2028. The UK's MHRA approval would likely follow the FDA decision, not lead it.

There is no real price, because there's nothing legitimate to buy yet — it isn't licensed anywhere, so no pharmacy, clinic or the NHS can sell or prescribe it. Any specific price you see quoted online is for an unlicensed product from an unregulated source, and should be treated as a red flag rather than a price to compare. Once retatrutide is eventually licensed, expect its private cost to sit somewhere near or above Mounjaro's current private pricing, given it's a more complex triple-receptor treatment — but that's an estimate, not a quote.

Several patterns show up again and again on unlicensed sellers: labelling the product "research use only" or "not for human consumption" while still giving human dosing instructions; no prescription, screening or consultation required before you can buy; payment only via WhatsApp, Telegram, crypto or bank transfer rather than a normal secure checkout; "limited time" discount codes or bulk-buy offers; branded as a "pen" or medical device despite having no medicines licence; and no GPhC (General Pharmaceutical Council) registration number you can independently verify on the GPhC register. Genuine UK pharmacies are always GPhC-registered and never sell an unlicensed medicine for personal use, no matter how the listing is worded.

The only lawful route anywhere in the world today is enrolling in an authorised clinical trial. In the UK, the NIHR's Be Part of Research service and the international ClinicalTrials.gov registry both let you search for currently-recruiting retatrutide trials near you. There is no purchase route, prescription route, or private-clinic route that is legitimate today — anything claiming otherwise is operating outside UK law.

In the TRIUMPH-1 phase 3 trial, the 12mg dose produced 28.3% average weight loss at 80 weeks, with continuers who started at BMI 35+ reaching up to 30.3% at 104 weeks. Other TRIUMPH trials in different populations (with diabetes, with cardiovascular disease, with knee osteoarthritis) reported 20.8% to 28.7%.

Trial data has also shown improvements in cardiovascular risk markers (cholesterol, blood pressure), knee osteoarthritis pain, liver fat (relevant to fatty liver disease), and blood sugar control in people with prediabetes.

Mostly gastrointestinal — nausea (up to 42.4% at the highest dose in TRIUMPH-1), diarrhoea, constipation and vomiting, worst during dose escalation. Discontinuation due to side effects rises with dose, from around 4% at the lowest tested dose to 11–14% at the highest.

The TRIUMPH protocol starts at 2mg weekly and steps up every 4 weeks — 2mg, 4mg, 6mg, 9mg, then 12mg maintenance from week 17. This is trial-protocol information, not a guide for using any unlicensed product.

On trial weight-loss percentage alone, yes — retatrutide's results are higher than either. But retatrutide's evidence base is much earlier-stage, with none of the years of real-world safety monitoring that Mounjaro and Wegovy already have, and neither is available in the UK yet regardless.

No. CagriSema is Novo Nordisk's own unlicensed candidate — a combination of semaglutide and an amylin analogue, a different mechanism to retatrutide's triple-receptor design. CagriSema has already been filed with the FDA, ahead of retatrutide in the regulatory queue.