The Peptide Directory

InvestigationalTriple GIP / GLP-1 / glucagon receptor agonistWeight loss

Retatrutide

Investigational — not FDA-approved. Lilly plans a US Biologics License Application in Q1 2027.

Last reviewed by The Peptide Directory Editorial Team

What is Retatrutide?

Retatrutide is an investigational once-weekly peptide from Eli Lilly that activates three receptors — GIP, GLP-1 and glucagon — and is in Phase 3 trials for obesity and related conditions; it is not FDA-approved.

Key takeaways

  1. Phase 2 (NEJM, 2023): up to 24.2% mean weight loss at 48 weeks on 12 mg.
  2. TRIUMPH-2 (type 2 diabetes): −12.7%, −19.1%, −20.8% at 80 weeks on 4, 9, 12 mg vs −4.0% placebo (Lilly, July 2026).
  3. TRIUMPH-3 (severe obesity + cardiovascular disease): −21.6% and −22.6% on 9 and 12 mg vs −3.2% placebo.
  4. Lilly says retatrutide "cannot be legally sold or marketed for human use".

What makes Retatrutide different?

It is the first "triple agonist" to reach Phase 3. The glucagon component is thought to raise energy expenditure and liver fat burning on top of the appetite effects of GLP-1 and GIP.

How does Retatrutide work?

GLP-1 and GIP activity reduce appetite and improve insulin response; glucagon-receptor activity increases energy expenditure and hepatic fat oxidation. Trials step the dose up every four weeks from 2 mg to limit GI side effects.

What the clinical evidence actually shows

  • Phase 2 (NEJM, 2023, 48 weeks): dose-dependent weight loss reaching a mean of 24.2% on 12 mg.
  • TRIUMPH-2 (NCT05929079): 1,152 adults with type 2 diabetes; 80-week weight change −12.7% (4 mg), −19.1% (9 mg), −20.8% (12 mg) vs −4.0% placebo; A1C down up to 1.6 points.
  • TRIUMPH-3 (NCT05882045): 1,949 adults with BMI ≥35 and cardiovascular disease; −21.6% (9 mg), −22.6% (12 mg) vs −3.2% placebo at 80 weeks.
  • A Phase 3 obesity paper was published in NEJM in 2026 (PMID 42814954).

How much research exists on Retatrutide?

PubMed indexes 202 papers mentioning Retatrutide in the title or abstract, 202 of them from the last five years and 10 tagged as clinical trials (search run October 19, 2026; repeat the search).

Most relevant recent papers

Registered clinical studies

ClinicalTrials.gov lists 33 studies with Retatrutide as an intervention (see all). Most recent:

Side effects

In TRIUMPH-2 the most common adverse events were diarrhea, nausea, constipation, decreased appetite and vomiting; dysesthesia (altered skin sensation) occurred in 4.5–7.3% vs 0.7% on placebo. Discontinuation for adverse events reached 11.6% (9 mg) in TRIUMPH-2 and 13.5% (12 mg) in TRIUMPH-3.

Regulatory & access status

  • Not FDA-approved. Lilly plans to submit a BLA in Q1 2027 after completing its manufacturing (CMC) package.
  • Not eligible for legal compounding; sales labeled "research use only" are not authorized for human use.

Sourcing & safety

There is no legal prescription source today. The only legitimate access route is enrollment in a clinical trial (search ClinicalTrials.gov).

Doses in labels and trials

Reference only — copied from published research. Not a recommendation.

SourceWhat it says
TRIUMPH-2 / TRIUMPH-3 designStart 2 mg weekly; step up every 4 weeks (2 → 4 → 6 → 9 → 12 mg) to target doses of 4, 9 or 12 mg.
Phase 2 (2023)Doses from 1 mg to 12 mg weekly over 48 weeks.

What the evidence does not show

  • Approval — no regulator has approved retatrutide.
  • A cardiovascular benefit: TRIUMPH-3 MACE hazard ratios had confidence intervals crossing 1.
  • Anything about the purity or identity of products sold online as "retatrutide".

Retatrutide FAQ

Is retatrutide FDA-approved?

No. Retatrutide is investigational. Lilly says it plans to submit a Biologics License Application to the FDA in Q1 2027.

How much weight did people lose on retatrutide?

Up to 24.2% at 48 weeks in Phase 2; in Phase 3 TRIUMPH-3, 22.6% on 12 mg at 80 weeks versus 3.2% on placebo.

Can I legally buy retatrutide?

Not as a medicine. Lilly states retatrutide cannot be legally sold or marketed for human use; clinical trials are the only legitimate access.

How does retatrutide differ from tirzepatide?

Retatrutide adds glucagon-receptor activity to the GIP and GLP-1 activity that tirzepatide has.

Related peptides & comparisons

TirzepatideSemaglutide Tirzepatide vs Retatrutide Weight Loss

References

  1. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial, N Engl J Med (2023), PMID 37366315
  2. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity, N Engl J Med (2026), PMID 42814954
  3. Lilly's triple agonist, retatrutide, successful in two additional Phase 3 obesity trials, Eli Lilly and Company (2026)
  4. TRIUMPH-2 (NCT05929079), ClinicalTrials.gov
  5. TRIUMPH-3 (NCT05882045), ClinicalTrials.gov

Retatrutide calculators

Lab arithmetic only: convert a mass to a volume or syringe units at a known concentration with the units converter, or work out a concentration with the reconstitution calculator.

There is no legal prescription route for Retatrutide today; clinical trials are the only legitimate access.

Get Retatrutide via telehealth

None of the telehealth providers we have verified lists Retatrutide.

Research suppliers that list Retatrutide

17 vendors in our directory listed a product matching Retatrutide in their public catalog on October 19, 2026. Listed alphabetically; a listing is not an endorsement. Research use only.

Prices per mg, where we could verify them, are on our price comparison.

Retatrutide dosing protocol

The published trial schedule is reproduced, with sources, on Retatrutide 12 mg in Phase 3: TRIUMPH Escalation Schedule.

Find clinics offering Retatrutide

No clinic in our verified directory lists Retatrutide yet.

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