Retatrutide (LY3437943)

Retatrutide is a triple-receptor agonist peptide developed by Eli Lilly. It simultaneously targets three metabolic receptors:

• GLP-1 (appetite suppression)
• GIP (insulin/metabolic regulation)
• Glucagon (calorie burning / energy expenditure)

This triple mechanism makes it more broadly acting than tirzepatide (dual GLP-1/GIP) or semaglutide (GLP-1 only).

Clinical Trial Results (2026)

Recent Phase 3 TRIUMPH trials have shown impressive results — the 12 mg arm averaged 28.3% weight loss at 80 weeks, and a higher-BMI subgroup reached 30.3% at 104 weeks. Eli Lilly also met primary endpoints in adults with type 2 diabetes (TRANSCEND-T2D-1). Peptidedosingprotocols

As of June 2026, retatrutide is NOT approved by the FDA, EMA, or any regulatory agency. It remains an investigational compound.

Dosing Protocol

It is administered by subcutaneous injection once per week, with a slow titration climbing every 4 weeks: 1 mg → 2 mg → 4 mg → 6 mg → 9 mg → 12 mg. Peptidedosingprotocols

The half-life is approximately 144 hours (6 days), which supports once-weekly dosing and reaches steady state within 4–5 weeks at each dose level. PeptideDeck

Available Vial Sizes & Prices (Research Grade)

Monthly Cost by Route

Reconstitution

Retatrutide comes as a lyophilized (freeze-dried) powder and must be reconstituted with bacteriostatic water before use — which is why the two topics are closely connected.

A common example: a 10 mg vial reconstituted with 2 mL of BAC water yields a concentration of 5 mg/mL.

Storage

Reconstituted retatrutide should be refrigerated at 2–8°C and used within 4–6 weeks. Unreconstituted powder can be stored at room temperature short-term, but refrigeration is better for longer storage. Never freeze the reconstituted solution.

Side Effects

Common side effects (especially at higher doses) include nausea, reduced appetite, and occasional vomiting — most are dose-dependent. Most people find 8 mg/week hits the efficacy sweet spot with tolerable side effects; pushing to 12 mg increases nausea for some without proportional additional benefit.