Retatrutide (Reta) UK: research peptide vials, 10 mg to 40 mg

In brief: ALTA PEPTIDES supplies Retatrutide (GLP-1 / GIP / glucagon triple receptor agonist) as a 40 mg lyophilised vial (in stock now; 10 mg, 20 mg, 30 mg vials coming soon) for £139.99 (£3.50/mg), with the certificate of analysis for lot 07022601 published, held in UK stock and dispatched the same working day before 1pm. Supplied for laboratory research only, not for human consumption.

New to Retatrutide? Read our guide, What is retatrutide? The triple-hormone peptide, explained simply, for what it is, what the research covers and how it is handled.

What is retatrutide?

Retatrutide (LY3437943) is an investigational 39-amino-acid peptide carrying a C20 fatty diacid side chain. It is a triple agonist: it activates the GLP-1, GIP and glucagon receptors at once, which is what separates it from semaglutide (GLP-1 only) and tirzepatide (GLP-1 and GIP). It was designed by Eli Lilly and is in phase 3 clinical trials for obesity, type 2 diabetes, obstructive sleep apnoea and knee osteoarthritis; five phase 3 trials have reported positive results, and Lilly plans to file with the FDA in early 2027. It has no marketing authorisation in any country.

We supply the synthetic retatrutide peptide in the UK as a lyophilised research reagent at 99%+ HPLC purity, in sealed 40 mg vials, with a certificate of analysis for every lot. It is a laboratory reagent for in-vitro research and is never supplied for human use.

Retatrutide vials, sizes and price

Retatrutide is listed here in four vial sizes: 10 mg (£49.99), 20 mg (£84.99), 30 mg (£114.99) and 40 mg (£139.99). The 40 mg vial is in stock now and dispatched the same working day; the retatrutide 10mg, 20mg and 30mg vials are out of stock and due back soon, so they show as out of stock in the size selector above until they land. The 40 mg vial gives the lowest retatrutide price per milligram (£3.50 per mg, against £5.00 for the 10 mg), and one 40 mg vial reconstituted in the laboratory covers an extended in-vitro programme from a single lot. The smaller retatrutide 10mg and 20mg vials suit shorter assays or method work where a whole 40 mg vial would sit reconstituted for longer than it should. Prices include VAT; delivery is free over £75. The same compound is also stocked as the Retatrutide Pen: a sealed Synedica pre-filled pen already loaded with 40 mg, supplied with needles, at £159.99 (£4.00 per mg); the vial remains the cheaper of the two per milligram.

The retatrutide cost per milligram here is a research-reagent price. It is not comparable with a licensed medicine price, and no part of it is priced for human use. Pay by debit or credit card, Apple Pay or Google Pay on a secure payment page, or by cryptocurrency at checkout. Orders placed before 1pm Monday to Friday leave the same day by Royal Mail Tracked 48.

Retatrutide pen or vial?

Searches for a retatrutide pen mostly turn up pre-filled injector pens. There is no licensed retatrutide pen anywhere in the world; the only ones inside a regulatory framework are those used in Eli Lilly's trials. Most of the pens sold by UK vendors are filled by the vendor itself from powder, with no manufacturer behind the device and no certificate for what is in the cartridge, and a vendor that fills and sells its own pens cannot honestly call them a research chemical.

What we stock, alongside this 40 mg vial, is the Synedica Retatrutide Pen: a sealed pre-filled multi-use pen from a named manufacturer, already loaded with 40 mg of retatrutide, boxed with needles and the manufacturer's leaflet, and supplied as received. We do not fill it. The retatrutide in it is from the same manufacturer lot as this vial (lot 07022601), so the same published certificate on our certificates page covers the compound in both. The vial is powder to reconstitute in the laboratory and is the cheaper of the two per milligram; the pen costs more because the device and the manufacturer's preparation are included, and there is nothing to reconstitute.

Retatrutide vs Mounjaro (tirzepatide) and semaglutide

Retatrutide vs Mounjaro is the comparison most people are searching for, so here is how the three compounds differ on the published record. Mounjaro is the brand name for tirzepatide, a licensed prescription medicine that acts on the GLP-1 and GIP receptors. Wegovy and Ozempic contain semaglutide, a licensed GLP-1 receptor agonist. Retatrutide adds the glucagon receptor to both, and is unlicensed.

On trial data, the phase 2 retatrutide study published in the New England Journal of Medicine in 2023 reported a mean body-weight reduction of 24.2% at 48 weeks in the highest-dose arm. The SURMOUNT-1 trial of tirzepatide reported 20.9% at 72 weeks, and the STEP 1 trial of semaglutide reported 14.9% at 68 weeks. These figures come from different trials with different populations and durations, so retatrutide vs tirzepatide is not a head-to-head result; Lilly's phase 3 TRIUMPH programme is what will settle it. None of this is a claim about our product, which is supplied for laboratory research only.

Retatrutide side effects reported in trials

The retatrutide side effects reported in the phase 2 trial were dose-dependent and mostly gastrointestinal: nausea, diarrhoea, vomiting and constipation, largely mild to moderate and most frequent while the dose was being escalated. Increases in heart rate were observed, along with skin sensitivity (dysaesthesia) in a minority of participants, and some withdrew because of adverse events. These are trial observations in a controlled clinical setting and are reproduced here for completeness of the scientific record. They are not a safety profile for any product on this site, and we do not give any guidance on human use.

Where to buy retatrutide online in the UK

Where to buy retatrutide online comes down to what a supplier can prove. Check for a certificate of analysis tied to the lot number on the vial (identity by mass spectrometry, purity by HPLC), sealed crimp-capped vials rather than loose or repackaged stock, cold-chain storage, UK dispatch rather than drop-shipping from overseas, and a research-use policy that is actually enforced. Be wary of any seller who describes retatrutide as a weight-loss product, fills its own pens from powder, publishes dosing schedules, or quotes a price per month rather than per milligram: those are the hallmarks of a supplier marketing an unlicensed medicine for human use, which is unlawful in the UK. Our retatrutide UK page summarises stock, testing and delivery in one place.

Our retatrutide vials are stocked in the UK, tested per lot, shipped in plain insulated packaging with a cool pack, and sold under a research use policy that we apply to every order.

Legal and regulatory position

Retatrutide is not a controlled substance in the UK and is legal to possess. It is an investigational medicine with no licence in any country; its licensed relatives semaglutide and tirzepatide are prescription-only. The MHRA actively pursues unlawful supply of GLP-1-class medicines for human use. This product is sold as a laboratory reagent on the basis of written legal advice, and is not supplied for human use under any circumstances. Correspondence indicating an intended human use results in the order being refused.

Reta: the short name

Reta is the shorthand that has attached itself to retatrutide in forums and search, so reta peptide, reta 40mg and reta UK all mean this compound. There is no separate product called reta. Anyone comparing retatrutide UK peptides across suppliers (retatrutide peptides are listed by a dozen UK vendors) should compare on the same basis: vial mass, lot-matched certificate, and UK stock, which is what this listing offers for a retatrutide peptide buy in the UK.

Retatrutide price (UK)

Prices include VAT. Shipping is £4.95 by Royal Mail Tracked 48, free on orders over £75, and sealed items can be returned within 14 days. Ships from UK stock with the lot certificate for the vial you receive. See how our price compares with every other UK vendor on the retatrutide price comparison.

Quality and testing

The certificate of analysis for lot 07022601 of Retatrutide is published on our certificates page and linked above. It is the manufacturer's QC batch certificate for the bulk lot the vials were filled from, reporting identity by mass spectrometry and purity by HPLC, with a purity result of 99.2%. ALTA's own independent third-party test of the finished vials from this lot is pending and will be published on the same row when it arrives. The lot number on the vial label matches the certificate. Specification: ≥ 99% (HPLC), supplied as lyophilised powder, 3 ml glass vial, sealed; 40 mg per vial in stock (10 mg, 20 mg and 30 mg vials coming soon).

Reconstitution and handling

Retatrutide arrives as a lyophilised cake under an aluminium crimp seal. Let the vial reach room temperature before opening so that condensation does not form on the powder. Swab the stopper with an alcohol swab, draw the chosen volume of bacteriostatic water (our bacteriostatic water guide explains why it is used rather than sterile water) with a sterile syringe, and add it slowly down the inside wall of the vial rather than onto the powder. Swirl gently until clear; never shake, which can denature the peptide. Label the vial with the date and concentration. The peptide calculator converts vial amount and diluent volume into concentration, millilitres and U-100 syringe units for any target amount. Sealed vial: 2 to 8 °C, protected from light. Reconstituted: 2 to 8 °C, use within 4 weeks.

Lot traceability

Every Retatrutide vial carries a printed lot number and expiry. The same lot number appears on the certificate of analysis for that lot on our certificates page, which names who issued it (the manufacturer's QC laboratory for a batch certificate, or the outside laboratory for a third-party report) so it can be checked directly. ALTA's own independent test of each lot is published on the same row as it arrives. If the number on your vial does not match a certificate on our site, contact support before using it. Certificates are kept online for the life of the product plus two years.

Related products

Retatrutide Pen, BPC-157, TB-500, and everything else in Weight & Metabolic or the full range. Reconstitution supplies: bacteriostatic water, insulin syringes and alcohol swabs.

Related reading in the Journal

• What is retatrutide? The triple-hormone peptide, explained simplyRetatrutide, often shortened to reta, is Eli Lilly's experimental once-weekly peptide that acts on three appetite and metabolism hormones at once: GLP-1, GIP and glucagon. In its largest phase 3 trial, people on the highest amount lost 28.3% of their body weight on average over 80 weeks. What it is, how it works, the results, the side effects and where it stands.
• Retatrutide pen vs vial: what UK vendors actually sellA pre-filled retatrutide pen and a lyophilised retatrutide vial are different products in handling, stability, traceability and price per milligram, and who filled the pen matters more than the format. What each one is and how the two we supply compare.
• How to get retatrutide in the UK: what is legal, the trial results, the release date and how to check a vendorRetatrutide is an unlicensed investigational compound sold in the UK as a research reagent. Where that leaves a buyer legally, what separates a credible vendor from a risky one, and what the market charges.
• Retatrutide vs tirzepatide vs semaglutide: receptors, licences and trial resultsOne licensed GLP-1 agonist, one licensed dual agonist, one unlicensed triple agonist: how the three differ on the published record.
• Apitegromab and bodybuilding: can a myostatin blocker really build muscle?Myostatin is the body's brake on muscle, and animals born without it are famously huge. That is why bodybuilders are curious about apitegromab, the first approved drug that blocks it. But in people, myostatin blockers have added only modest muscle, rarely more strength, and none has ever been tested in healthy or trained adults. What the evidence really shows, the risks, and why it is banned in sport.

Handling and buying guides: How to reconstitute peptides: a laboratory guide, How to store peptides, and how long lyophilised peptides last at room temperature, How to read a peptide certificate of analysis.

Handling and storage

Sealed vial: 2 to 8 °C, protected from light. Reconstituted: 2 to 8 °C, use within 4 weeks. Keep sealed until use. Allow the vial to reach room temperature before opening to avoid condensation on the powder. Reconstitute with bacteriostatic water added slowly down the wall of the vial; do not shake. Our calculator covers the arithmetic.