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Retatrutide

Also known as: LY3437943, Reta
FDA: Not FDA-approved WADA: Not specifically listed

Retatrutide (LY3437943) is a 39-amino-acid triple hormone receptor agonist developed by Eli Lilly that simultaneously activates the GIP, GLP-1, and glucagon receptors. It represents the next evolution in incretin-based obesity therapeutics — moving from single agonism (Semaglutide) to dual agonism (Tirzepatide) to triple agonism. Phase 2 data published in the New England Journal of Medicine showed up to 24.2% body weight reduction at 48 weeks — the highest weight loss reported for any anti-obesity drug at its stage of development. Currently in Phase 3 trials (TRIUMPH program), with 133 PubMed publications as of April 2026. The addition of glucagon receptor

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Molecular weight 4,882.56 Da
Half-life ~6 days 144
CAS number —
Route Subcutaneous
02

Mechanism

Triple agonist — simultaneously activates GIP, GLP-1, and glucagon receptors for maximal metabolic effects including appetite suppression, insulin sensitization, and direct fat oxidation

03

Dosing

DOSE RANGE 1000–12000 mcg
FREQUENCY 1x weekly
CYCLE LENGTH Ongoing (titrate from 1mg to 12mg weekly over ~24 weeks)

Titration: 1mg (wk 1-4) → 2mg (wk 5-8) → 4mg (wk 9-12) → 8mg (wk 17-20) → 12mg (wk 21+). Based on Phase 2 protocol. Phase 3 may refine dosing.

04

Research summary

Study Type Year Key Finding
Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial Phase 2 RCT (dose-finding, double-blind, placebo-controlled) 2023 24.2% mean body weight loss with retatrutide 12mg at 48 weeks
Obesity Pharmacotherapy Reimagined: The Era of Multi-Receptor Agonists and Next-Generation Metabolic Modulators Review / Perspective 2026 Multi-receptor agonists (dual and triple) represent a paradigm shift in obesity treatment
Multi-omic Profiling Reveals Retatrutide Alleviates Adipose Tissue Fibrosis via Metabolic Reprogramming and Tissue Repair Preclinical study (multi-omic analysis, animal model) 2026 Retatrutide reduces adipose tissue fibrosis through metabolic reprogramming
Glucagon receptor agonism in the treatment of obesity and diabetes review 2009 Glucagon receptor agonism increases energy expenditure via thermogenesis
A Study of Retatrutide in Participants With Type 2 Diabetes, Obesity, and Obstructive Sleep Apnea — — —
A Study of Retatrutide in Participants With Obesity and Knee Osteoarthritis — — —
A Study of Retatrutide in Participants With Obesity and Chronic Low Back Pain — — —
Retatrutide Phase 2 Trial in MASLD — Liver Fat Reduction with Triple Agonist Therapy RCT 2024 Retatrutide reduced liver fat by >80% at highest dose
Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial RCT 2023 Retatrutide 12mg produced 24.2% mean weight loss at 48 weeks
Retatrutide, a GIP, GLP-1 and Glucagon Receptor Agonist, for People with Type 2 Diabetes: A Randomised, Double-Blind, Placebo and Active-Comparator Controlled, Parallel-Group, Phase 2 Trial RCT 2023 HbA1c reduction up to -2.02% with retatrutide 12mg
05

Stacking & interactions

Gut protection during GLP-1-mediated GI side effects

Lean mass preservation during aggressive weight loss

GH axis support to counter lean mass loss

06

Sourcing

Current prices

Updated today

10mg

Only vendor stocking this size on the VialBase roster.

Size unspecified

Only vendor stocking this size on the VialBase roster.

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What bloodwork do I need?

Reference ranges are general guidelines. Consult your physician for interpretation.

PRE-CYCLE
  • CMP
  • CBC
  • Lipid Panel
  • Fasting Glucose
  • HbA1c
  • Fasting Insulin
  • Amylase
  • Lipase
  • Thyroid Panel (TSH, Free T3, Free T4)
DURING CYCLE
  • Fasting Glucose
  • HbA1c
  • Lipid Panel
  • Amylase
  • Lipase
  • TSH
POST-CYCLE
  • CMP
  • Lipid Panel
  • Fasting Glucose
  • HbA1c
  • Thyroid Panel
Safety & Regulatory Status
FDA STATUS Not FDA-approved. Phase 3 clinical trials underway (Eli Lilly — TRIUMPH program)
WADA STATUS Not specifically listed (covered under S0 as non-approved substance)

Regulatory status for Retatrutide may change. Verify current status with your jurisdiction before use. This is not legal or medical advice.

Frequently Asked Questions

What is Retatrutide?
Retatrutide (development code LY3437943) is an investigational triple receptor agonist — it activates the GLP-1, GIP, and glucagon receptors at once. Being developed by Eli Lilly, it is the next step beyond dual GIP/ GLP-1 drugs like tirzepatide. The added glucagon-receptor activity is thought to increase energy expenditure. It is not FDA-approved and remains in clinical trials.
How does Retatrutide work?
Retatrutide engages three receptors with complementary effects. The GLP-1 and GIP arms suppress appetite, slow gastric emptying, and improve insulin response — similar to tirzepatide. The added glucagon-receptor agonism is proposed to raise energy expenditure and promote fat oxidation, including in the liver. The net effect in trials is large weight loss, though the mechanism is still being characterized.
How effective is Retatrutide for weight loss?
In a Phase 2 trial published in 2023, retatrutide produced up to 24.2% mean body-weight loss at 48 weeks at the highest dose in adults with obesity (PMID 37366315) — among the largest reductions reported for a single agent. These are Phase 2 results; Phase 3 trials (Eli Lilly's TRIUMPH program) are ongoing and will determine confirmed efficacy and safety.
How is Retatrutide dosed?
Retatrutide is not FDA-approved and is not available as a compounded or prescription product, so there is no validated clinical dose. The Phase 2 protocol titrated from 1 mg weekly upward over roughly 24 weeks toward 8–12 mg. Material sold by research-peptide vendors is not quality-assured. No retatrutide dosing should be considered medical advice.
What are Retatrutide's side effects?
As an investigational drug, its safety profile is still being defined. In Phase 2 the side effects were predominantly gastrointestinal — nausea, vomiting, and diarrhea — and were dose-related, consistent with the incretin drug class. Long-term safety, the impact of glucagon-receptor activation on glucose, and rarer risks remain under study in ongoing Phase 3 trials.
Is Retatrutide FDA-approved or legal?
No. Retatrutide is an investigational compound in Phase 3 trials and is not FDA-approved or otherwise authorized for clinical use. It is sold only as a research chemical, with variable purity and authenticity. As a non-approved substance it falls under WADA's S0 category. It is not a legally marketed medicine in any jurisdiction.

References

  1. Jastreboff AM, Kaplan LM, Frías JP, et al.. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine (2023). PMID: 37366315
  2. Lempesis IG, Dalamaga M. Obesity Pharmacotherapy Reimagined: The Era of Multi-Receptor Agonists and Next-Generation Metabolic Modulators. Metabolism Open (2026). PMID: 41948476
  3. Li Q, Cheng W, Zhang J, et al.. Multi-omic Profiling Reveals Retatrutide Alleviates Adipose Tissue Fibrosis via Metabolic Reprogramming and Tissue Repair. Diabetology & Metabolic Syndrome (2026). PMID: 41964043
  4. Day, J.W., Ottaway, N., Patterson, J.T. et al.. Glucagon receptor agonism in the treatment of obesity and diabetes. Nature Reviews Drug Discovery (2009). PMID: 19381150
  5. A Study of Retatrutide in Participants With Type 2 Diabetes, Obesity, and Obstructive Sleep Apnea.
  6. A Study of Retatrutide in Participants With Obesity and Knee Osteoarthritis.
  7. A Study of Retatrutide in Participants With Obesity and Chronic Low Back Pain.
  8. Sanyal, A.J., Kaplan, L.M., Frias, J.P. et al.. Retatrutide Phase 2 Trial in MASLD — Liver Fat Reduction with Triple Agonist Therapy. New England Journal of Medicine (2024). PMID: 38858523
  9. Jastreboff, A.M., Kaplan, L.M., Frias, J.P. et al.. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine (2023). PMID: 37351564
  10. Rosenstock, J., Frias, J.P., Jastreboff, A.M. et al.. Retatrutide, a GIP, GLP-1 and Glucagon Receptor Agonist, for People with Type 2 Diabetes: A Randomised, Double-Blind, Placebo and Active-Comparator Controlled, Parallel-Group, Phase 2 Trial. Lancet (2023). PMID: 37385280