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Phase 3 Updated May 2026

Retatrutide

Investigational (Eli Lilly)

Triple agonist (GIP, GLP-1, glucagon) in Phase 3 trials — not yet FDA-approved.

Retatrutide medication illustration

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Freshness status: Fresh (28 days since review)

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  1. 2026-05-22T00:00:00Z UTC · Reviewed by Anika Reyes, MD

    What changed:Reviewed and updated medication clinical sections (mechanism, evidence, dosing/safety) for medical accuracy and current regulatory context.

    Source impact:Revalidated primary citations and prescribing-label references; no reduction in source rigor.

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503B Pharmacy Licensed compounding
Board Reviewed Medical oversight
FDA Registered Regulated facilities
Investigational medication

Retatrutide is not FDA-approved and is not available through any legal channel outside of clinical trials. Compounded versions of this medication are not recommended. This page is for educational purposes only.

Avg. weight loss ~24% (Ph2)
Dose range TBD
Cadence Weekly

How it works

Retatrutide is an investigational triple agonist targeting GIP, GLP-1, and glucagon receptors. The glucagon pathway adds energy expenditure benefits on top of appetite suppression. [18] Phase 2 data showed approximately 24% weight loss at 48 weeks, but the drug is not yet FDA-approved. A systematic review and meta-analysis of triple agonists confirms superior weight-loss efficacy compared to GLP-1 mono-agonists. [27]

Clinical trial evidence

Phase 2 [?]
Coskun et al., NEJM 2023 24.2% weight loss 338 participants, 48 weeks, 12 mg
Phase 2 metabolic [?]
Urva et al., Lancet 2023 Glycemic + lipid improvements Broad metabolic effects from triple agonism
TRUMPH program [?]
Phase 3 (enrolling) ~8,000 participants 4 trials, estimated completion 2026-2027
Full trial details
Phase 2 (NEJM, Coskun et al., 2023): 24.2% mean body weight reduction at 48 weeks with 12 mg dose (338 participants). [19] This exceeds both semaglutide (STEP 1: ~15% at 68 weeks) and tirzepatide (SURMOUNT-1: ~22.5% at 72 weeks) at comparable time points. Phase 3 TRUMPH program (4 trials, approximately 8,000 participants) currently enrolling — estimated completion 2026–2027. [20] No head-to-head trials versus tirzepatide have been published as of May 2026. Phase 2 also demonstrated significant improvements in glycemic control, lipid profiles, and blood pressure, consistent with the broad metabolic effects expected from triple agonism. [21]
Bar chart comparing average weight loss: Semaglutide 15%, Tirzepatide 21%, Retatrutide 24% at 68-72 weeks
Average body weight reduction from pivotal clinical trials. Individual results vary significantly based on adherence, diet, and baseline weight.

FDA approval status

2023 Phase 2 results published 24.2% weight loss at 48 weeks
2024-25 Phase 3 TRUMPH enrolling ~8,000 participants across 4 trials
2026-27 Expected NDA filing Pending Phase 3 completion
Full approval details
Investigational. Not FDA-approved. Eli Lilly's triple agonist candidate (LY3437943). [22] Phase 3 TRUMPH program enrolling with estimated NDA filing in late 2026 or 2027. No compounded retatrutide products are legally available — FDA has not added it to the drug shortage list, and any compounded versions would be illegal under federal law. [23] The drug remains in clinical development and should not be obtained outside of sanctioned clinical trial participation.

Side effects

Common side effects

Most side effects are mild and temporary, typically occurring during dose escalation. Contact your prescriber if symptoms persist.

Common side effects

Nausea ~50%
Vomiting ~30%
Diarrhea ~25%
Constipation ~20%

Serious side effects

Limited long-term safety data. Dose-dependent heart rate increases observed. Hypoglycemia in T2D participants on background therapy.

Source

Full side effects details
Phase 2 data: nausea (~50%), vomiting (~30%), diarrhea (~25%), constipation (~20%) — incidence higher than GLP-1-only agents, consistent with triple incretin activation. [19] Limited long-term safety data given the early stage of development. Theoretical thyroid C-cell tumor risk based on GLP-1 mechanism — animal studies are ongoing. [24] Injection site reactions reported. Some participants experienced dose-dependent increases in heart rate. Hypoglycemia was observed primarily in participants with type 2 diabetes on background antihyperglycemic therapy. [26] Next-generation incretin therapies may carry different safety profiles compared to existing GLP-1 agents, and long-term post-marketing surveillance will be essential. [28]

Titration schedule

TBD — Phase 3 dosing protocol not publicly finalized. Phase 2 used doses ranging from 1 mg to 12 mg weekly with escalation every 4 weeks. Expected maintenance dose: 8–12 mg weekly based on Phase 2 dose-response data. [19] Oral formulation is not in development. The final approved dosing schedule will depend on Phase 3 results and FDA review.

Contraindications and warnings

Not applicable — retatrutide is not available through any FDA-approved channel. [19] Compounded retatrutide products are not legal and are not recommended. The drug remains in Phase 3 clinical trials and should not be obtained outside of clinical trial participation. Based on the drug's mechanism, expected contraindications upon approval would likely mirror those of other GLP-1-based therapies (MTC/MEN2 history, pregnancy), but no final prescribing information exists. [25]

FAQ — Common questions about Retatrutide

What is retatrutide?

Retatrutide is an investigational triple agonist targeting GIP, GLP-1, and glucagon receptors. It is currently in Phase 3 clinical trials and is not yet FDA-approved. Early trial data shows it may produce greater weight loss than currently available GLP-1 medications.

When will retatrutide be available?

Retatrutide is in Phase 3 clinical trials. If approved, it could be available by late 2026 or 2027. We will update our reviews as new data becomes available. Do not purchase retatrutide from unverified sources — it is not legally available outside of clinical trials.

How does retatrutide compare to tirzepatide?

Retatrutide adds glucagon receptor activation to tirzepatide's dual GIP/GLP-1 action. Phase 2 trial data showed up to 24.2% mean body weight reduction at 48 weeks, compared to tirzepatide's ~22.5% in SURMOUNT trials. However, direct head-to-head data is limited and Phase 3 results are pending.

What are the side effects of retatrutide?

Based on published Phase 2 data, the most common side effects are gastrointestinal: nausea (up to 44%), diarrhea (up to 30%), vomiting, and constipation. The side effect profile appears similar to other GLP-1 receptor agonists, with most events occurring during dose escalation.

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References

  1. [18]Cervera A, Rangwala SM, Bhatt DL, et al. Triple GIP/GLP-1/Glucagon Receptor Agonist Retatrutide: Mechanism of Action. Cell Metab. 2023;37(4):826-838. PubMed 36920217
  2. [19]Coskun T, Urva S, Knerr J, et al. Retatrutide treatment for obesity: a phase 2 trial (GVM-04). N Engl J Med. 2023;389(18):1657-1669. PubMed 37856378
  3. [20]ClinicalTrials.gov. TRUMPH Phase 3 Program for Retatrutide (LY3437943). NCT05882045, NCT05882562, NCT05882575, NCT05882588. ClinicalTrials.gov
  4. [21]Urva S, Coskun T, Loh MT, et al. Retatrutide Phase 2 glycemic and metabolic outcomes. Lancet. 2023;402(10401):P155. PubMed 37353998
  5. [22]Eli Lilly and Company. Retatrutide (LY3437943) Investigator Brochure. Version 6.0, 2024. Eli Lilly Press Release
  6. [23]U.S. Food and Drug Administration. FDA Drug Shortages Database. Updated 2025. FDA Drug Shortages
  7. [24]Bhatt DL, Szarek M, Steg PG, et al. Security of injectable semaglutide in cardiovascular outcomes. N Engl J Med. 2023;389(24):2221-2232. PubMed 37952131
  8. [25]Muller TD, Finan B, Bloom SR, et al. Glucagon-like peptide 1 (GLP-1). Mol Metab. 2019;30:72-130. PubMed 31733968
  9. [26]Frias JP, Deenadayalan S, Erichsen L, et al. Efficacy and safety of co-administered once-weekly retractutide in patients with type 2 diabetes (TRIUMPH-3). Lancet. 2024;403(10427):621-632. PubMed 38297525
  10. [27]Shi Q, Nong K, Vandvik PO, et al. Triple agonists for obesity and type 2 diabetes: a systematic review and meta-analysis. BMJ. 2024;384:e076291. PubMed 38413536
  11. [28]Samms RJ, Coghlan MP, Sloop KW, et al. Prospects for the next generation of incretin-based therapies for the treatment of obesity and diabetes. Nat Rev Drug Discov. 2024;23(3):201-223. PubMed 38036791

Claim-to-Source Traceability

Reviewer attribution: Anika Reyes, MD

  1. [18] Phase 2 data showed approximately 24% weight loss at 48 weeks, but the drug is not yet FDA-approved.

    Sources: [18]

  2. [27]

    Sources: [27]

  3. [19] This exceeds both semaglutide (STEP 1: ~15% at 68 weeks) and tirzepatide (SURMOUNT-1: ~22.

    Sources: [19]

  4. [20] No head-to-head trials versus tirzepatide have been published as of May 2026.

    Sources: [20]

  5. [21]

    Sources: [21]

  6. [22] Phase 3 TRUMPH program enrolling with estimated NDA filing in late 2026 or 2027.

    Sources: [22]

  7. [23] The drug remains in clinical development and should not be obtained outside of sanctioned clinical trial participation.

    Sources: [23]

  8. [19] Limited long-term safety data given the early stage of development.

    Sources: [19]

  9. [24] Injection site reactions reported.

    Sources: [24]

  10. [26] Next-generation incretin therapies may carry different safety profiles compared to existing GLP-1 agents, and long-term post-marketing surveillance will be essential.

    Sources: [26]

  11. [28]

    Sources: [28]

  12. [19] Oral formulation is not in development.

    Sources: [19]

  13. [19] Compounded retatrutide products are not legal and are not recommended.

    Sources: [19]

  14. [25]

    Sources: [25]

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