Retatrutide Pen (Reta Pen): Synedica pre-filled pen, 40 mg

In brief: ALTA PEPTIDES supplies Retatrutide Pen as a sealed Synedica pre-filled pen containing 40 mg, supplied with needles for £139.99 (£3.50/mg), with the certificate of analysis for lot 07022601 published for the retatrutide loaded in the pen, held in UK stock and dispatched the same working day before 1pm. Supplied for laboratory research only, not for human consumption.

New to Retatrutide Pen? Read our guide, Retatrutide pen vs vial: what UK vendors actually sell, for what it is, what the research covers and how it is handled.

What is the retatrutide pen?

This is the Synedica Retatrutide Pen, supplied sealed exactly as it leaves the manufacturer. Each box contains one pre-filled multi-use pen already loaded with 40 mg of retatrutide, a set of disposable pen needles, and the manufacturer's leaflet. It is a finished pre-filled device: there is nothing to reconstitute and no diluent is required, which is the difference from our 40 mg lyophilised vial, where the compound arrives as freeze-dried powder for the laboratory to reconstitute. It is the product that searches for a retatrutide pen UK stock, a retatrutide 40mg pen or a synedica retatrutide pen point at, the only retatrutide pre-filled pen we supply, and we supply it strictly as a laboratory reagent for research use.

The retatrutide loaded in the pen is from manufacturer lot 07022601, the same lot as our 40 mg vial, and the certificate of analysis for that lot (the manufacturer's QC batch certificate: purity 99.2% by HPLC, identity by infrared spectrum, HPLC retention time and molecular ion mass) is published on our certificates page and linked from this page. The certificate covers the lot of retatrutide the pen was loaded from; the filling is the manufacturer's, and the Synedica device, needles and leaflet are supplied as received. We do not open, repackage or relabel pens, and the manufacturer's packaging and leaflet do not form part of our product description.

Pen versus the 40 mg vial

Both listings contain the same synthetic retatrutide and the same total, 40 mg. The 40 mg vial is a single lyophilised vial from a lot whose certificate of analysis we publish, and it is the cheaper of the two per milligram: £109.99 (£2.75 per mg) against £139.99 (£3.50 per mg) for the pen. The vial is powder to be reconstituted in the laboratory, which leaves concentration and diluent under the researcher's control. The pen is a sealed manufacturer-prepared device with the compound already loaded and needles included, so there is no handling of powder; the higher price reflects the device and the manufacturer's preparation. The retatrutide in the pen is from the same lot as the vial (lot 07022601), so both ship under the same published lot certificate. Both are supplied for laboratory research only. Anyone comparing a retatrutide 40mg listing on price should use the retatrutide price comparison, which lists UK vendors per vial and per milligram.

What the research covers

Retatrutide (LY3437943) is an investigational 39-amino-acid peptide carrying a C20 fatty diacid side chain. It is a triple agonist of the GLP-1, GIP and glucagon receptors, which 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. The phase 2 obesity trial 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, with gastrointestinal adverse events the most common. It has no marketing authorisation in any country. Our trial results and release date guide and comparison with tirzepatide cover the trial record; none of it is a claim about this product, which is supplied for laboratory research only.

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 pen is sold as a laboratory reagent and is not supplied for human use under any circumstances. It is a sealed product from a named manufacturer with a published lot certificate for the retatrutide in it, not a pen filled by us or by an unnamed vendor. The pen is supplied as received from the manufacturer, and the manufacturer's leaflet is not our product information. Correspondence indicating an intended human use results in the order being refused, as set out in our research use policy.

Buying the retatrutide pen in the UK

The pen is held in UK stock and dispatched the same working day before 1pm Monday to Friday by Royal Mail Tracked 48, in plain insulated packaging with a cool pack. It is in stock. Pay by debit or credit card, Apple Pay or Google Pay on a secure payment page, or by cryptocurrency at checkout. It is priced per pen, and delivery is free over £100 so every pen ships free. As a finished third-party product it does not count towards the peptide stack discount. The retatrutide pen is one of two retatrutide formats we stock; the 40 mg vial is the other. Our retatrutide pen UK guide explains how to tell a sealed manufacturer pen from a vendor-filled one.

Contents and pricing

Prices include VAT. Shipping is £4.95 by Royal Mail Tracked 48, free on orders over £100, and sealed items can be returned within 14 days. Ships from UK stock with the lot certificate for the retatrutide loaded in your pen (lot 07022601). See how our price compares with every other UK vendor on the retatrutide price comparison.

Quality and testing

Retatrutide Pen is a finished, sealed product from a third-party manufacturer (Synedica): a pre-filled multi-use pen already loaded with 40 mg of retatrutide, boxed with disposable needles and the manufacturer's leaflet. The retatrutide loaded in the pen is from manufacturer lot 07022601, the same lot as our 40 mg retatrutide vial, and the certificate of analysis for that lot is published on our certificates page and linked above: the manufacturer's QC batch certificate for the bulk lot, reporting identity by mass spectrometry and purity by HPLC, with a purity result of 99.2%. The certificate is for the lot of compound the pen was loaded from; the filling is the manufacturer's. The Synedica pen, needles and leaflet are supplied sealed as received, and we do not open, repackage or relabel pens. ALTA's own independent test is published: Janoshik Analytical tested a sealed pen from lot 07022601 on 9 October 2026, confirmed its identity and reported 99.752% purity by HPLC. The report can be checked with the lab (task #240684; verify at verify.janoshik.com with key D63SKHBAB6TV). Specification: Manufacturer specification (Synedica); retatrutide from lot 07022601, certificate published.

Format and handling

Retatrutide Pen is a sealed pre-filled pen supplied ready-prepared by the manufacturer; there is nothing to reconstitute and no diluent is required, and no powder is handled. Keep it refrigerated at 2 to 8 °C, protected from light, and capped between uses, within the manufacturer's stated in-use period. The Synedica pen, needles and leaflet are the manufacturer's and are supplied as received; they are not our product information. Sealed: 2 to 8 °C, protected from light. Do not freeze. Keep the pen capped between uses and within the manufacturer's in-use period.

Batch traceability

Every pen and its box carry the manufacturer's printed batch number and expiry. The retatrutide loaded in the pen is from lot 07022601, and that lot number appears on the certificate of analysis on our certificates page, which names who issued it (the manufacturer's QC laboratory) so it can be checked directly; it is the same certificate that covers our 40 mg retatrutide vial. ALTA has also had a sealed pen from this lot tested independently, and that report is published on the same certificates page. We supply pens sealed and do not open or relabel them, so the filling and the device are the manufacturer's. If the batch number on your pen does not match what is published on our site, contact support before using it.

Related products

Retatrutide, 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.

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: 2 to 8 °C, protected from light. Do not freeze. Keep the pen capped between uses and within the manufacturer's in-use period.