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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

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10mg

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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.

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: 37385275
  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: 38856224
  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