Medications
What is retatrutide?
An overview of retatrutide — an investigational triple-hormone agonist being studied for obesity and metabolic disease, and why it is not yet available by prescription.
6 min read · Updated 2026-05-24
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What retatrutide is
Retatrutide is an investigational peptide developed by Eli Lilly.
It is a triple agonist: it activates three receptors at once — GLP-1, GIP, and glucagon.
Why three receptors matter
GLP-1 reduces appetite and improves blood sugar control.
GIP appears to amplify GLP-1's effects and may help with fat metabolism.
Glucagon, perhaps counterintuitively, can increase energy expenditure when paired with the other two.
Combining all three is the working theory behind why retatrutide has shown larger weight loss in trials than single- or dual-agonist drugs.
Where it is in development
Retatrutide is in Phase 3 clinical trials as of 2024-2025.
Phase 2 results published in the New England Journal of Medicine reported substantial average weight reduction at the highest doses studied.
It is not FDA-approved and is not available by prescription anywhere in the world.
Why the name keeps appearing online
Vials labeled as retatrutide are being sold by so-called research peptide vendors. These products are not regulated as medicines, are not verified for identity or purity, and are not legal to use as drugs.
Coverage of trial results has driven interest well ahead of any approval.
Key takeaways
- Retatrutide is an investigational triple agonist (GLP-1 + GIP + glucagon).
- It is in Phase 3 trials and is not FDA-approved.
- Products sold online as ''retatrutide'' are unregulated and not the same as the trial drug.
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