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Incretin and metabolic research Research use only

Retatrutide

Investigational triple agonist of GIP, GLP-1 and glucagon receptors (LY3437943)

An investigational medicine from Eli Lilly that activates three hormone receptors at once. It has completed several Phase 3 trials but, as of October 2026, it is not approved anywhere. Research-grade powder sold online is not Lilly's product and has not been checked by any regulator.

Reviewed 26 October 2026 · Sources listed at the end of the page

Structure

A lipidated peptide built on the GIP backbone and tuned to activate three receptors: GIP, GLP-1 and glucagon. Like semaglutide and tirzepatide it carries non-standard amino acids and a fatty acid chain for a long half-life.

Evidence at a glance

Where the published research on Retatrutide comes from, by type of study.

Several studies

Cell studies

Receptor activation profiles at GIP, GLP-1 and glucagon receptors.

Several studies

Animal studies

Energy expenditure and body weight in rodent models.

Phase 2 and 3 trials

Human studies

Phase 2 results were published in 2023; several Phase 3 trials reported results from December 2025 to September 2026.

Worth knowing. Retatrutide is the most heavily enforced research peptide in 2026. FDA warning letters named sellers of it, often under code names such as GLP-3 or RT.

Research areas

What laboratories have studied Retatrutide for, and in which models. These are research questions, not proven uses.

Triple receptor agonism

Receptor signalling assays

Combines GIP and GLP-1 effects with glucagon receptor activation, which raises energy expenditure.

Energy expenditure

Rodent obesity models

Studied for effects on liver fat and energy use in animals.

Clinical development

Phase 3 trial programme

Studied in obesity, type 2 diabetes, knee osteoarthritis and sleep apnoea trials.

Legal status

Retatrutide is an investigational medicine. Research-grade material may be sold only for laboratory research, and regulators actively enforce against sellers who market it for people.

United States Not approved

Investigational and not FDA-approved as of October 2026. FDA has issued warning letters to sellers of research retatrutide.

United Kingdom Not licensed

No MHRA licence. Sold with medicinal claims it counts as a medicine under the Human Medicines Regulations 2012.

European Union Not authorised

No EMA authorisation. Under Directive 2001/83/EC a substance can be a medicine by function, whatever its label says.

Sport Check S0

Not yet approved, so it may fall under WADA's S0 non-approved substances class. Check the current list.

Licensed medicines

There is no licensed medicine containing Retatrutide yet. People interested in it can ask a clinician about clinical trials or approved alternatives such as semaglutide or tirzepatide.

Lab handling

General good practice for research materials. Follow the supplier's datasheet where it differs.

Storage

Keep the sealed material at −20 °C, dry and away from light. Let the vial reach room temperature before opening to stop condensation.

Solubility

Research grade is usually soluble in sterile water or dilute buffer. Add solvent down the vial wall and swirl gently rather than shaking.

Aliquots

Split solutions into single-use aliquots, label with lot number and date, and freeze. Avoid repeated freeze-thaw cycles.

Work out your stock solution

Stock concentration, molarity and dilutions for Retatrutide, using MW 4731 g/mol.

Open the lab calculator

Before you buy for your lab

Tick each check as you confirm it with the supplier. Do not order until all six are done.

Batch-specific COAThe certificate shows the lot number printed on the vial.
Named third-party labThe testing lab is named and can confirm the report on its own site.
Identity and purityHPLC purity and mass-spec identity both reported, with the measured mass close to about 4731.
No human-use marketingNo doses, injection guides, before-and-after claims or syringe kits on the site.
No FDA warning letterSearch the supplier's name on the FDA warning letters page.
Research buyer confirmationThe supplier asks you to confirm research or institutional use.

0 of 6

RecommendedPasses all six checks and sells no GLP-1 research compounds.

CautionResearch-only marketing and COAs, but sells GLP-1 or other closely watched compounds.

AvoidDosing or human-use claims, or an FDA warning letter. Never linked.

Supplier comparison for Retatrutide is in progress. Every supplier of research-grade Retatrutide carries at least a Caution label, because regulators focus on this class. Labels follow our editorial policy. Until listings go live, run any supplier through the vendor check. All products from any supplier are for laboratory research use only.

Questions researchers ask

What is Retatrutide?

What is the molecular weight of Retatrutide?

About ≈4731 g/mol. Use the figure on your batch certificate of analysis.

Is Retatrutide approved for human use?

No. Investigational and not FDA-approved as of October 2026. FDA has issued warning letters to sellers of research retatrutide.

How should Retatrutide be stored in the lab?

Keep the sealed material cold, dry and away from light, typically at −20 °C. Once in solution, split it into single-use aliquots and freeze to avoid repeated freeze-thaw cycles.

Does this page give doses?

No. We publish laboratory and educational information only, never doses, injection guidance or treatment advice.

Sources

For research and educational purposes only. Retatrutide is not approved for human or veterinary use. Some links on this site are affiliate links. · Disclosure · Disclaimer · Editorial policy · Contact · Privacy policy · © 2026 Peptides in Lab