Retatrutide pen: what it is, price and where to buy it

The retatrutide pen is a pre-filled injector pen that AuraVia Research sells as a research product. Its cartridge already holds retatrutide in solution. There is no powder to dissolve and no separate solvent: the cartridge is sealed at the factory, and the pen has a graduated dial mechanism. The design copies the insulin pens that diabetes care has used for decades (Pearson, 2010): a plastic body, a sealed cartridge, a cap and a dial.

The vendor lists two sizes: 10 mg and 20 mg of retatrutide per pen. It states refrigerated storage, between 2 and 8 °C, and provides a certificate of analysis (CoA) for each batch. On the purity, AuraVia's page about its pen range states 99% or higher, but the product page of the retatrutide pen shows no figure today. The reference is therefore the purity stated on the CoA of your batch. Our product data does not include the volume of solution in the cartridge: check it on the label.

The compound itself is an investigational molecule. Retatrutide was developed by Eli Lilly as a triple agonist of the GIP, GLP-1 and glucagon receptors. It is in phase 3 clinical trials and it is not approved as a medicine anywhere in the world. The pen format does not change that status, even if the product looks like an Ozempic or Mounjaro pen. We explain the difference in the section on legal status.

This page describes the product, compares the two formats and lists the checks to make before buying. It gives no usage information, no amount to inject and no protocol.

AuraVia Research sells retatrutide in two formats: the pre-filled pen and the vial of lyophilised powder (freeze-dried). The compound is the same. What changes is the form in which it is stored, the price and what you have to do before an experiment. Prices below were checked on October 19, 2026, VAT included.

At the prices of October 19, for the same amount, the pen costs about 54% more than the vial in the 10 mg size and about 59% more in the 20 mg size. At list prices, without the current promotion, the gap rises to 92% and 95%. In both formats, the 20 mg size has the lower price per mg. Prices and promotions change often: always check the current price on the vendor's site before you order.

Stability is the main technical difference. Reference reviews on protein pharmaceuticals show that a molecule in solution undergoes more degradation reactions (oxidation, aggregation, hydrolysis) than the same molecule in the dry state (Wang, 1999). This is why the industry freeze-dries fragile proteins (Wang, 2000). The powder in a vial is the more robust form for storage. The pen avoids the reconstitution step, but it needs an unbroken cold chain, from the warehouse to your refrigerator.

• Vial: the powder has to be put into solution before any experiment, with a solvent and sterile material. Before reconstitution, the powder tolerates storage better. It is the cheaper format per mg.
• Pen: nothing to prepare, but storage at 2 to 8 °C at all times, a shorter shelf life to watch, and a higher price per mg.

For the same comparison across the seven pens sold in Europe, see our guide to pre-filled peptide pens and vials.

In our checks on October 19, 2026, only one vendor sells a retatrutide pen: AuraVia Research, based in the European Union. Here are the facts we checked on its site:

• Warehouse in the EU, prices VAT included.
• Standard tracked shipping in 3 to 5 working days, for €9, free on orders from €150.
• Delivery area: European Union only.
• Certificate of analysis per batch, with purity measured by HPLC.
• Batch number printed on the label, so you can match the pen with its CoA.

The links to AuraVia Research on this page are affiliate links: if you order through them, Klow Peptide may receive a commission, at no extra cost to you. The facts above do not depend on it, and we update them when the vendor's site changes.

AuraVia does not deliver outside the European Union. Readers in other countries can compare vial vendors, delivery areas and certificates of analysis on our page where to buy retatrutide.

Retatrutide, known during development as LY3437943, is a synthetic peptide developed by Eli Lilly. It is designed to activate three receptors at once: the GIP receptor, the GLP-1 receptor and the glucagon receptor. For this reason it is described as a triple agonist. Its preclinical characterisation, with activity on all three receptors in cell and animal models, was published in 2022 (Coskun et al., 2022).

In humans, the published data come from regulated clinical trials, run under medical supervision:

• a randomised, double-blind, placebo-controlled phase 2 trial in 338 adults with obesity or overweight, followed for 48 weeks (Jastreboff et al., 2023, New England Journal of Medicine);
• a phase 2 trial in people with type 2 diabetes, against placebo and an active comparator (Rosenstock et al., 2023, The Lancet);
• a randomised phase 2a study on liver fat in metabolic dysfunction-associated steatotic liver disease, or MASLD (Sanyal et al., 2024, Nature Medicine).

The most common adverse events reported in these trials were gastrointestinal: nausea, vomiting, diarrhoea and constipation. A modest rise in heart rate was also observed. Phase 2 trials are small and short. They test a concept; they do not establish efficacy or long-term safety. Eli Lilly's phase 3 programme, called TRIUMPH, is under way to answer those questions.

Regulatory status: retatrutide is not approved by the FDA, by the EMA or by any other regulator. It remains an investigational compound, and nothing on this page is a promise of effect. Our complete retatrutide guide details the mechanism, the trials and the regulatory timeline.

You check a pen the same way as a vial, with extra points that come from the solution form.

• Batch and CoA match: the batch number on the certificate of analysis must be the one printed on the pen or on the box. A generic CoA that is not tied to a batch tells you nothing about your pen.
• HPLC purity: read the figure and the date of the analysis on the batch CoA. For this pen, the CoA is the reference, because the product page shows no figure.
• Cold-chain shipping: a product in solution should travel in insulated packaging. Ask the vendor how it ships, and put the pen in the refrigerator as soon as it arrives.
• Complete label: amount of peptide, volume of solution, batch number and expiry date.
• Sealed cartridge: the seal is intact and the pen shows no sign of opening. A cloudy solution or visible particles are a reason to contact the vendor.
• “Research use only” statement: a serious vendor does not present its pen as a medicine or as a treatment.

An unusually low price should make you suspicious. A pen needs a cartridge, a mechanism and cold shipping: it costs more to produce than a vial. A retatrutide pen sold well below the price of the vial deserves extra checks.

In the European Union, the retatrutide pen is sold as a research product. According to the vendor, it is intended for laboratory research only and not for human use. It is not a medicine and has no marketing authorisation, neither from the EMA in Europe nor from the FDA in the United States. Retatrutide itself is still in phase 3 trials and is not approved anywhere.

Do not confuse it with pharmaceutical incretin pens. Ozempic and Wegovy (semaglutide) or Mounjaro (tirzepatide) are approved medicines: they are made under pharmaceutical control, prescribed by a doctor and dispensed by pharmacies, with a patient leaflet and medical follow-up. A research pen looks similar, but it is a different thing: no approval, no prescription, no medical supervision and no regulatory guarantee on its manufacturing.

Rules on buying and importing research compounds vary from country to country, and the EU-wide status above does not replace national law. Check the rules that apply to you before any order. This page is for information only and gives no medical advice: for any question about weight or diabetes, talk to a doctor.