Retatrutide
Retatrutide (LY3437943)
Triple GLP-1/GIP/glucagon agonist
About
Eli Lilly's triple-agonist peptide that activates GLP-1, GIP and glucagon receptors simultaneously. Phase 3 trials show 24%+ weight loss after 48 weeks — the largest weight loss seen with any GLP-1-class drug to date.
Mechanism
Triple activation: GLP-1 (appetite suppression + insulin), GIP (insulin sensitivity), glucagon (energy expenditure and lipolysis).
Dosage
Draw to 20 units on a U-100 insulin syringe
10 mg · 1 mL BAC
When to take: Same weekday each week, independent of meals. Best in the morning or evening.
Reconstitution
Vial size (mg): 10 mg · BAC water (mL): 1 mL · Concentration: 10 mg/mL
Can be stored refrigerated after reconstitution for up to 4 weeks.
Dosing reference
Units to draw at the typical dose range, per vial size.
| Vial | Water | Typical draw |
|---|---|---|
| 10 mg | 1 mL | 20–120 units |
| 12 mg | 1 mL | 16.5–100 units |
| 24 mg | 1 mL | 8.5–50 units |
Benefits
- Largest weight loss among GLP-1 class drugs
- Improved glycemic control
- Increased energy expenditure
- Cardioprotective effects (preliminary)
Side effects
- Nausea and vomiting (common initially)
- Diarrhea and constipation
- Headache
- Possible pancreatitis (rare)
Gender notes
Cautions
- Pregnancy and breastfeeding
- History of pancreatitis
- Medullary thyroid carcinoma (MEN2)
- Severe gastroparesis
Research
- Jastreboff et al: Retatrutide phase 2 obesity trial
New England Journal of Medicine · 2023
338 adults with obesity. 24% weight loss at 48 weeks on 12 mg weekly — more than semaglutide or tirzepatide.
- TRIUMPH-1 phase 3 results (interim)
Eli Lilly press release · 2024
Eli Lilly Phase 3 program, 2024 interim data.