In this article11 sections
Not as a medicine: it is not licensed anywhere, so no doctor can prescribe it and no pharmacy can dispense it. It is sold in the UK only as a laboratory research reagent. Lilly has now reported five positive phase 3 trials and plans to file with the US regulator in early 2027; a UK licence would come after that.
People searching for how to get retatrutide in the UK usually arrive with a mixture of trial headlines and forum posts and no clear picture of what is legal, what is for sale, or what a fair price looks like. This article answers those questions plainly, along with what the trials have shown and when it could be released. Retatrutide is an investigational compound with no licence anywhere, it is sold in the UK only as a laboratory reagent, and the difference between a credible vendor and a risky one comes down to a short list of checks. Nothing here is guidance on using the compound; that is the vendor's line and it is ours.
- Retatrutide has no marketing authorisation in the UK or anywhere else; it is in trials run by Eli Lilly.
- It is not a controlled drug under the Misuse of Drugs Act; it is sold as a laboratory reagent for research use only.
- Supplying it for human use, or describing use in people, is an offence for the vendor under the Human Medicines Regulations 2012.
- In September 2026, tested 40 mg vials from UK vendors cost £139.99 to £154; smaller vials cost more per milligram.
- Check for a lot-matched , a named testing laboratory, UK stock, and a registered company before buying.
What is retatrutide, and when will it be available?
In shortA weekly injection being tested by Eli Lilly that acts on three appetite and metabolism hormones. Not approved anywhere yet; Lilly plans to apply in early 2027.
- 2023Phase 2 published
24.2% average weight loss at 48 weeks in 338 adults, NEJM.
- Dec 2025First phase 3: TRIUMPH-4
28.7% at 68 weeks in adults with obesity and knee osteoarthritis.
- May 2026TRIUMPH-1
28.3% at 80 weeks; 45.3% of people on the top dose lost 30% or more.
- Jul 2026TRIUMPH-2 and TRIUMPH-3
20.8% with type 2 diabetes, 22.6% with heart disease. Five positive phase 3 trials.
- Q1 2027Planned FDA filing
Lilly's stated plan. US review usually takes around a year.
- LaterUK licence, then NICE
MHRA authorisation and a NICE appraisal are separate steps before any NHS use.
Lilly press releases, Dec 2025, 21 May 2026 and 23 Jul 2026; Jastreboff et al., NEJM 2023.
Retatrutide (LY3437943) is a 39-amino-acid peptide developed by Eli Lilly that activates three receptors at once: , and glucagon. It is in phase 3 trials as of 2026, following results published in the New England Journal of Medicine in 2023. It has no marketing authorisation from the MHRA, the EMA or the FDA, which means no doctor can prescribe it, no pharmacy can dispense it, and no company can sell it as a medicine. The trial results are set out below, and our comparison with tirzepatide puts it in context with the licensed compounds.
What have the retatrutide trials shown?
In shortFive big trials: up to 28.7% average weight loss. Feeling sick is the main side effect.
Average body-weight loss at the highest dose tested in each trial. Phase 2: Jastreboff et al., NEJM 2023. TRIUMPH-4: Lilly, Dec 2025. TRIUMPH-1: Lilly, 21 May 2026 (efficacy estimand). TRIUMPH-2 and TRIUMPH-3: Lilly, 23 Jul 2026. Topline company figures; full papers pending.
Share of participants over 80 weeks. Lilly, 21 May 2026.
The phase 2 obesity trial, published in the New England Journal of Medicine in June 2023, randomised 338 adults with obesity (BMI 30 or more), or overweight (BMI 27 to under 30) with at least one weight-related condition, without diabetes, to placebo or one of several retatrutide doses for 48 weeks. Mean body-weight change at 48 weeks was minus 8.7% at the lowest dose (1 mg), minus 17.1% at 4 mg, minus 22.8% at 8 mg and minus 24.2% at 12 mg, against minus 2.1% for placebo, and weight was still falling when the study ended. A parallel phase 2 in type 2 diabetes, published in The Lancet, reported HbA1c reductions of up to about 2 percentage points alongside weight loss.
Lilly began phase 3 in 2023 with the TRIUMPH programme for obesity and TRANSCEND for type 2 diabetes, more than 5,800 participants in the core obesity trials alone. Five have now reported positive topline results. TRIUMPH-4, in adults with obesity and knee osteoarthritis, came first in December 2025: 28.7% average weight loss at 68 weeks on the highest dose. TRIUMPH-1, the main obesity trial of 2,339 adults without diabetes, reported on 21 May 2026: 19.0%, 25.9% and 28.3% average weight loss at 80 weeks across the three doses, against 2.2% on placebo, with 45.3% of people on the top dose losing 30% or more of their body weight. In an extension for people with a starting BMI of 35 or more, weight loss reached 30.3% at 104 weeks. TRIUMPH-2 (obesity with type 2 diabetes) and TRIUMPH-3 (severe obesity with established heart disease) reported on 23 July 2026: up to 20.8% and 22.6% at 80 weeks.
The side-effect pattern matched the rest of the class: nausea, diarrhoea, constipation and vomiting were the most common, mostly mild to moderate and most frequent while the dose was being stepped up. In TRIUMPH-1, 11.3% of people on the top dose stopped because of side effects, against 4.9% on placebo. Dysaesthesia, an altered or uncomfortable skin sensation, was reported in up to 12.5% against 0.9% on placebo; Lilly described these events as generally mild to moderate and mostly resolving during treatment. These are company topline figures from press releases; the full peer-reviewed papers are still to come.
When will retatrutide be released in the UK?
In shortLilly plans to apply in the US in early 2027. The UK decision comes separately, after that.
There is no retatrutide release date yet, because there is no approved product. Lilly said on 23 July 2026 that it now has the clinical data to support submissions for obesity, knee osteoarthritis pain and obstructive sleep apnoea, and that it plans to file with the US Food and Drug Administration in the first quarter of 2027, once its manufacturing data package is complete. A standard FDA review takes around a year, although Lilly's oral GLP-1 orforglipron was approved in 50 days under a priority voucher in 2026, so the US timing could move. The UK is a separate decision: the MHRA must grant a marketing authorisation, and NICE must then appraise it before any NHS use. Until all of that happens, every retatrutide vial outside Lilly's trials is unlicensed, and anyone selling it as an approved medicine, or as "the next Mounjaro" available early, is misdescribing it.
Is retatrutide legal to buy in the UK?
In shortBuying it as a research chemical isn't a crime. Selling it for people to use is.
Not in the Misuse of Drugs Act schedules.
As a research reagent.
No licence, so no GP or pharmacy can supply it.
Human Medicines Regulations 2012.
Border Force can hold it if it looks like a medicine.
Evidence of supply for human use.
Summary of the legal position set out in this section. Not legal advice.
Retatrutide is not a controlled drug. It does not appear in the Misuse of Drugs Act schedules, so possession is not an offence and neither is buying it. What the law regulates is supply as a medicine: under the Human Medicines Regulations 2012 a vendor may not sell an unlicensed product for human use, and the MHRA treats advertising, dosing advice and presentation for injection as evidence of that intent. The consequence is a market in which retatrutide is sold as a research reagent, labelled for laboratory use only, and in which any vendor who tells you how to use it is breaking the rules that keep the product legal to sell. Our guide to UK peptide law goes through the regulations in detail. Customs is a separate question: importing from outside the UK exposes the parcel to seizure if Border Force judges it a medicine, which is one reason to buy from UK stock.
How much does retatrutide cost in the UK?
In shortA tested 40 mg vial costs about £140 to £154 in the UK: £3.50 to £3.85 per mg.
Interactive. Band: tested 40 mg vials from UK vendors cost £3.50 to £3.85 per mg in September 2026; 10 mg vials about £5.00 per mg.
Pounds per milligram, from the prices in this section (£180 to £220 a year earlier, £139.99 to £154 now).
On our September 2026 check, tested 40 mg retatrutide vials from UK vendors cost between £139.99 and £154, which is £3.50 to £3.85 per milligram; 10 mg vials at £49.99 work out at £5.00 per milligram. Prices have fallen from £180 to £220 a year earlier as supply has caught up. A price far below that band usually means an untested lot, a nominal amount that has not been verified, or a pen the vendor filled itself. Our price comparison lists every UK vendor we could verify and is rebuilt monthly.
How do you check a retatrutide vendor?
In shortFive quick checks tell a real supplier from a risky one.
Interactive. The five checks from this section; nothing is sent anywhere.
Five checks separate the credible from the rest, and a vendor that passes all five is rare enough to be worth paying a little more for.
A certificate from a named laboratory. The certificate of analysis should name the testing laboratory, the method (HPLC for purity, mass spectrometry for identity) and the result, and it should carry the lot number. "Third-party tested" with no document, or a certificate from the manufacturer alone, does not meet the bar. Our guide to reading a certificate shows what a real one looks like.
Lot matching. The lot number on the certificate must be the lot number on the vial you receive. A certificate for a lot the vendor sold six months ago proves nothing about the vial in your hand.
UK stock. Same-day or next-day dispatch from a UK address, a UK returns address, and Royal Mail or a named courier tracking. Two-week delivery windows mean the vendor is ordering after you pay.
A registered company. A company number you can look up at Companies House, a real trading address, and a support email that gets answered by a person. Vendors that exist only as a Telegram handle are not vendors.
No human-use language. A listing that talks about results, protocols or effects in people is a vendor who does not understand the line it is trading on, and it is the same vendor whose stock gets seized and whose site disappears. Research-use-only labelling is not a formality; it is the test of whether the business will still be there next month.
Which warning signs mean walk away?
In shortSix warning signs. One on its own isn't proof; two or three together is.
Human-use framing.
On the certificate.
Mounjaro or Wegovy imagery.
No card or bank transfer.
Bought or seeded.
Registered in the last few months.
From this section. None proves a problem on its own.
Prices quoted per month or per course, which is human-use framing. Certificates with the laboratory name blanked out. Stock photographs of licensed pens. Payment only by cryptocurrency with no card or bank option. Reviews that all appeared in the same week. A domain registered in the last few months. None of these is proof of a problem on its own; two or three together are.
Where is retatrutide sold in the UK?
In shortOnline research-chemical sellers, as powder vials or pre-filled pens.
Company number, UK address, same-day dispatch, lot-matched certificates.
Orders from a supplier abroad after you pay; long delivery windows.
Resells whatever it can source; rarely a certificate for your lot.
Categories as described in this section.
Research-chemical vendors, online, almost exclusively. Some are UK registered companies holding UK stock; some are drop-shippers with a UK domain and a supplier in China; some are marketplaces reselling whatever they can source. The product comes in two formats. A vial is dry powder, sealed, to be reconstituted in a laboratory. A pre-filled pen is the compound already in solution in an injector device, and the question to ask is who filled it: a sealed pen from a named manufacturer, such as the Synedica pen we stock, carries a batch number and can be traced to a published lot, whereas a pen the vendor filled itself from powder has no manufacturer behind it and no certificate for what is in the cartridge. Our pen versus vial article sets out the difference. Vial sizes on the UK market are 10, 20, 30 and 40 mg, and the 40 mg vial is the cheapest per milligram everywhere it is sold. For what we hold ourselves, with live prices and the lot certificate, see retatrutide in UK stock.
Everything above is the quick version. The sections below go deeper.
How to read trial results carefully
In shortTrial numbers are averages under close supervision, and the full papers aren't out yet.
Two cautions apply to every number above. Phase 2 results were in a few hundred people over 48 weeks; phase 3 results are in thousands over longer periods (80 weeks in TRIUMPH-1), so the two sets of figures are not directly comparable. And weight loss in a trial where participants are monitored, counselled and titrated is not a description of what a compound does in any other setting. Both cautions are part of the scientific record and belong alongside the headline figures.
What ALTA PEPTIDES supplies
In shortA tested 40 mg vial and a sealed pen, for lab research only.
We list retatrutide as a sealed 40 mg lyophilised vial at £139.99, each lot published with its certificate of analysis on our certificates page (the manufacturer's batch certificate today, our own independent test being added), and as the Synedica Retatrutide Pen at £159.99, a sealed pre-filled 40 mg pen with needles from a named manufacturer, supplied as received, the retatrutide in it from the same published lot as the 40 mg vial. The vial is powder to reconstitute and the cheaper of the two per milligram; the pen has nothing to reconstitute and the price includes the device. We do not fill pens ourselves. Both are held in UK stock and dispatched the same working day before 1pm. It is supplied for laboratory research only under our research use policy, and we decline orders where correspondence indicates any other intent. Our UK buying checklist covers the same ground for every compound we sell.
Questions people ask
Is it legal to buy retatrutide in the UK?
Buying it as a research reagent is not an offence; it is not a controlled substance. The legal exposure sits with a vendor that supplies it for human use or advertises it that way. Nothing on this site or in this article is guidance on use in people.
Can a GP or pharmacy supply retatrutide?
No. It is not a licensed medicine and is not available on prescription in the UK. The clinics and pharmacies that supply GLP-1 treatments supply licensed products such as Mounjaro and Wegovy.
Where is retatrutide sold in the UK?
By research-chemical vendors, online, as lyophilised vials and increasingly as pre-filled pens, some sealed from a named manufacturer and many filled by the vendor itself. Our price comparison page lists the vendors we could verify.
What does retatrutide cost in the UK?
Between £139.99 and £154 for a tested 40 mg vial at the time of writing, or £3.50 to £3.85 per milligram. Pens are priced differently and are a different product.
Information, not advice. This article summarises published research; nothing here is guidance on human or veterinary use. Products are sold under our research use policy.
