# Retatrutide

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- Published: 2026-08-28
- Author: Best Health IQ
- Summary: A triple agonist targeting GIP, GLP-1, and glucagon receptors — showing up to 24.2% weight loss in Phase II trials.
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### Retatrutide (LY3437943) A triple agonist targeting GIP, GLP-1, and glucagon receptors — showing up to 24.2% weight loss in Phase II trials. \*\*Category:\*\* Metabolic & Weight · \*\*Evidence:\*\* Strong Evidence · \*\*Status:\*\* Research Only ### Description Retatrutide (LY3437943) is an investigational triple agonist developed by Eli Lilly that simultaneously activates GIP, GLP-1, and glucagon receptors. It represents the next frontier in incretin-based obesity pharmacotherapy. In Phase II trials (TRIUMPH-1), retatrutide demonstrated up to 24.2% mean body weight reduction at 48 weeks — the highest weight loss ever reported for a pharmacological agent in a controlled trial. This surpasses both semaglutide and tirzepatide, establishing retatrutide as a potential best-in-class agent. The addition of glucagon receptor agonism to the dual GIP/GLP-1 mechanism is believed to drive additional energy expenditure through thermogenesis and hepatic glucose regulation, contributing to the superior weight loss outcomes. ### Key Characteristics - \*\*Molecular Formula:\*\* C228H352N50O70 - \*\*Molecular Weight:\*\* 4941.5 Da - \*\*Half-Life:\*\* ~6 days - \*\*Administration Routes:\*\* Subcutaneous injection (weekly) - \*\*Typical Dose:\*\* 1–12 mg weekly - \*\*Frequency:\*\* Once weekly ### Investigated Benefits - Up to 24.2% weight loss (Phase II) - Highest weight loss of any pharmacological agent in trials - Improved glycemic control - Potential cardiovascular benefits - Increased energy expenditure \_Benefits based on preclinical/animal research unless otherwise noted.\_ ### Mechanism of Action “A triple agonist targeting GIP, GLP-1, and glucagon receptors — showing up to 24.2% weight loss in Phase II trials.” Retatrutide’s triple receptor mechanism operates through three complementary pathways. GLP-1 receptor activation (shared with semaglutide) provides appetite suppression through hypothalamic circuits, slows gastric emptying, and stimulates glucose-dependent insulin secretion. GIP receptor activation (shared with tirzepatide) enhances the incretin effect, improves insulin sensitivity, and has direct effects on adipose tissue metabolism. The addition of glucagon receptor agonism is the key differentiator: glucagon receptor activation in the liver increases hepatic glucose output (counterbalanced by the insulin-stimulating effects), promotes lipolysis in adipose tissue, and — most importantly — stimulates thermogenesis by activating brown adipose tissue (BAT) and promoting uncoupled mitochondrial respiration. This thermogenic effect increases basal energy expenditure, which combined with the appetite suppression from GLP-1R and GIPR activation, produces the exceptional weight loss observed in trials. Phase III trials (TRIUMPH program) are ongoing. ### Dosing & Protocol - \*\*Typical Dose:\*\* 1–12 mg weekly - \*\*Frequency:\*\* Once weekly - \*\*Cycle Length:\*\* Ongoing (Phase III trials) - \*\*Administration:\*\* Subcutaneous injection (weekly) \*\*Protocol Notes:\*\* Currently in Phase III clinical trials. Requires physician supervision. Titrate slowly to minimize GI side effects. Not yet commercially available. ### Reconstitution Guide Per compounding pharmacy instructions ### Storage Information Refrigerate (2–8°C). Do not freeze. ### Quality & Sourcing Standards When sourcing Retatrutide for research purposes, the following quality benchmarks should be verified before use. - \*\*Purity:\*\* \>98% (verified by HPLC) - \*\*Certificate of Analysis (COA):\*\* Must be provided by supplier - \*\*Endotoxin Testing:\*\* \<0.1 EU/mg (prevents bacterial contamination) - \*\*GMP Compliance:\*\* Manufactured in cGMP-certified facility - \*\*Third-Party Testing:\*\* Independent lab verification preferred ### Research Highlights 1. Phase II: 24.2% weight loss at 48 weeks (highest ever in pharmacological trials) 2. Significant HbA1c reduction in T2DM 3. Phase III trials (TRIUMPH program) ongoing ### Evidence Level \*\*Strong Evidence\*\* — Multiple randomized controlled trials with high confidence in efficacy and safety data. ### Compatible Peptides No specific stacking recommendations for Retatrutide. ### FDA Disclaimer The statements made within this website have not been evaluated by the US Food and Drug Administration. The products and information provided are not intended to diagnose, treat, cure, or prevent any disease. This website is intended for educational and research purposes only. Many peptides described on this site are not approved by the FDA for human therapeutic use and are classified as research chemicals. Nothing on this site constitutes medical advice.