Investigational GIP / GLP-1 / glucagon triple agonist
Retatrutide
Investigational triple agonist - not approved, and barred from compounding
Retatrutide is an investigational drug developed by Eli Lilly that acts on three receptors at once - GIP, GLP-1, and glucagon. The glucagon arm is what distinguishes it from tirzepatide's dual action, and it is the main reason the compound attracts so much attention: early trial results reported weight reductions larger than those seen with existing medicines.
It is also the single most misrepresented compound sold online. Retatrutide is not approved anywhere in the world and has no brand name. As of September 2026 it cannot be legally purchased, prescribed, or compounded. Anything sold as 'retatrutide' is a research chemical produced outside the studied supply chain, not the medicine used in the trials.
Regulatory status
Retatrutide is not FDA-approved and is not approved by any other regulator. On 1 September 2026 the FDA prohibited retatrutide and cagrilintide from compounding, stating that they are not components of FDA-approved drugs and have not been found safe and effective for any condition. Because retatrutide was never approved, compounding with it was never lawful. The only legitimate access routes are enrolment in a clinical trial or, since August 2026, a limited expanded-access programme with strict eligibility criteria.
Mechanism
Three receptors, one molecule
GIP and GLP-1 agonism drive the appetite and glucose effects seen across this drug class. The addition of glucagon receptor agonism is proposed to increase energy expenditure, which is the mechanistic difference from tirzepatide.
Why the glucagon arm matters
Glucagon receptor activation raises energy expenditure but also tends to raise blood glucose. How the three activities balance in practice is a central question in the clinical programme.
Investigational status
Everything published describes trial populations under protocol, with defined doses, monitoring, and exclusion criteria. Those conditions are part of the intervention and are not reproducible outside a trial.
Research status
Lilly has reported results from the Phase 3 programme in obesity and type 2 diabetes, with weight reductions that drew widespread attention. Phase 2 results were published in a major journal in 2023. Trial results are not the same as an approved product: efficacy and safety are assessed by a regulator against the full dataset, and Lilly has said it plans to submit a biologics licence application in the first quarter of 2027. Review typically takes ten to twelve months, so approval, if granted, would not be expected before late 2027 at the earliest.
Verifying a batch
- 01If a listing offers retatrutide for sale, it is not the medicine from the trials - the trials supply is not available commercially.
- 02Ask what evidence supports the claimed identity. For an unapproved molecule there is no reference standard to compare against, which makes independent verification harder than for an established compound.
- 03Be sceptical of certificates for a compound with no approved reference material; confirm which laboratory issued it and whether the method is stated.
- 04Treat any dosing information circulating online as unsourced. No established human dose-response relationship exists for this molecule outside trial protocols.
Search lab reports for this compound →How purity is tested →
Questions
Is retatrutide FDA approved?+
No. As of September 2026 it is investigational, with no approval anywhere in the world. Lilly has said it plans to file in the first quarter of 2027, so approval would not be expected before late 2027.
Can I buy retatrutide legally?+
No. The FDA has stated it cannot be legally purchased, prescribed, or compounded. On 1 September 2026 the agency prohibited it from compounding entirely.
Is retatrutide sold online the real thing?+
No. Products sold under the name are research chemicals from unregulated supply chains, not the medicine used in Lilly's trials. There is no approved commercial supply for them to come from.
How can I access it legitimately?+
Through a clinical trial, or the limited expanded-access programme Lilly announced in August 2026, which has strict eligibility criteria. Both require going through a clinician.
How is retatrutide different from tirzepatide?+
Tirzepatide acts on two receptors, GIP and GLP-1. Retatrutide adds glucagon receptor agonism, which is proposed to increase energy expenditure. Tirzepatide is approved; retatrutide is not.
Related compounds
All compounds listed here are supplied for laboratory research use only and are not medicines, supplements, or products for human consumption.