Retatrutide dosage and protocol
Retatrutide (LY3437943) is an investigational triple GIP/GLP-1/glucagon receptor agonist from Eli Lilly and is not approved for any indication. In a 48-week phase 2 trial in adults with obesity, the highest dose produced a mean weight reduction of about 24 percent, and no head-to-head comparison with other agents had been completed.
- Vial size: 10 mg
- Reconstitution: 1 mL bacteriostatic water
- Concentration: 10.0 mg/mL
- Administration: subcutaneous
Research areas
- Fat Loss
- Weight Management
- Metabolic Research
- Glucose Regulation
- Body Recomposition
- GLP-1 Agonist
- Triple Agonist
Quick start
- Reconstitute: Add 1.0 mL bacteriostatic water → ~10.0 mg/mL concentration
- Typical weekly range: 2–8 mg once weekly (gradual escalation over 8–12 weeks)
- Easy measuring: At 10.0 mg/mL, 1 unit = 0.01 mL ≈ 100 mcg on a U-100 syringe
- Storage: Lyophilized at −20°C; after reconstitution, refrigerate at 2–8°C for up to 4 weeks
Dosing protocol
| Phase | Dose | Frequency | Volume |
|---|---|---|---|
| Weeks 1–4 | 2 mg (2000 mcg) | Once weekly (SC) | 0.20 mL (20 units) |
| Weeks 5–8 | 4 mg (4000 mcg) | Once weekly (SC) | 0.40 mL (40 units) |
| Weeks 9–12 | 6 mg (6000 mcg) | Once weekly (SC) | 0.60 mL (60 units) |
| Weeks 13+ | 8 mg (8000 mcg) | Once weekly (SC) | 0.80 mL (80 units) |
How it works
Retatrutide (LY3437943) is an investigational once-weekly injectable peptide from Eli Lilly that activates three receptors: GIP, GLP-1 and glucagon. GLP-1 and GIP activation reduce appetite, slow gastric emptying and enhance glucose-dependent insulin release, while glucagon receptor activation is thought to increase energy expenditure and fat oxidation, particularly in the liver. Combining all three is intended to produce greater weight loss than single or dual agonists. In a 48-week phase 2 trial in adults with obesity, the highest dose produced mean weight reduction of about 24 percent, larger than reported in earlier trials of semaglutide or tirzepatide, though no head-to-head comparison had been completed at that time. Phase 2 studies also showed improvements in HbA1c in type 2 diabetes and marked reductions in liver fat. A phase 3 programme (TRIUMPH) is assessing obesity, diabetes, sleep apnoea, knee osteoarthritis and cardiovascular outcomes, with early readouts reported to show substantial weight loss. Retatrutide is not approved for any indication as of this writing. Its long-term safety, including effects of glucagon agonism on heart rate and lean mass, is still being studied, and it should not be described as superior to approved drugs until comparative trials report.
Reconstitution steps
- Draw 1.0 mL bacteriostatic water with a sterile syringe
- Inject slowly down the vial wall; avoid foaming
- Gently swirl/roll until dissolved (do not shake)
- Label with reconstitution date and refrigerate at 2–8°C (35.6–46.4°F), protected from light; use within 4 weeks
Storage
Store lyophilized powder at -20°C. After reconstitution, refrigerate at 2-8°C and use within 28 days.
Important notes
- Investigational triple agonist with no completed head-to-head comparison against approved drugs
- Triple receptor agonist: GIP + GLP-1 + Glucagon, a distinct mechanism
- Phase 2 trial: about 24 percent mean body weight reduction at the highest dose (48 weeks)
- Research use only, not yet approved for human use
- Gradual dose escalation required to minimize GI side effects
- Store properly to maintain peptide integrity
Supplies
- Peptide vial (Retatrutide, 10mg)
- Bacteriostatic water
- Insulin syringes (U-100)
- Alcohol swabs