Retatrutide

Metabolic & weight Investigational (in clinical trials)

GLP-1 / GIP / glucagon triple agonist · also known as LY3437943

For reference only — not medical advice. Figures are commonly reported values compiled from published sources and may be wrong or out of date. Many compounds listed are not approved for human use. Talk to a licensed clinician before using any compound.

Retatrutide is an investigational triple agonist targeting the GLP-1, GIP, and glucagon receptors. Adding glucagon-receptor activity is studied for additional energy-expenditure effects on top of the incretin actions.

Commonly reported dosing (40 mg vial)

Reconstituted with 2 mL → 20 mg/mL.

Also sold in 5 mg, 10 mg, 20 mg, 30 mg, 50 mg, 60 mg vials.

Phase	Dose	Volume	U-100 units
Starting Weeks 1-4	2 mg	0.1 mL	10
Standard Weeks 5-8	4 mg	0.2 mL	20
Higher Weeks 9-12 in the phase 2 lower-start arm	8 mg	0.4 mL	40
Maximum studied Week 13 onward	12 mg	0.6 mL	60

Frequency: Once weekly, subcutaneous · Half-life: ~6 days

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Commonly reported dose escalation

Weeks	Dose	Volume	U-100 units
Weeks 1-4	2 mg	0.1 mL	10
Weeks 5-8	4 mg	0.2 mL	20
Weeks 9-12	8 mg	0.4 mL	40
Week 13+	12 mg	0.6 mL	60

Higher steps may need a larger vial or more than one draw. Escalation schedules vary; dosing decisions belong to a licensed clinician.

Commonly reported reconstitution steps

Vials are usually brought to room temperature (about 15-20 minutes) first.
2 mL of bacteriostatic water is added slowly down the inside wall of the 40 mg vial.
The vial is swirled gently until clear, not shaken.
This gives 20 mg/mL. Mixed vials are typically labeled with the date and refrigerated.

Storage

Before mixing: Sealed vials are commonly stored refrigerated (2-8 °C) and protected from light, or frozen for long-term storage.

After mixing: Reconstituted solution is commonly kept refrigerated (2-8 °C), protected from light, and not frozen.

Commonly used within 28 days of mixing.

How it works

The three-receptor profile combines appetite and insulin effects (GLP-1/GIP) with glucagon-driven increases in energy expenditure, a combination under active research.

Researched for

In the phase 2 obesity trial (48 weeks), mean weight change was -17.1% (4 mg), -22.8% (8 mg) and -24.2% (12 mg) versus -2.1% with placebo.
Triple-agonist mechanism studied for metabolic endpoints, with a phase 3 programme in obesity and type 2 diabetes.
Gastrointestinal adverse events in the phase 2 trial were dose-related and more frequent during escalation.

Notes

Investigational; trial protocols escalated the dose gradually.
The phase 2 obesity trial's lower-start 12 mg arm stepped 2, 4, 8 then 12 mg every 4 weeks, and the phase 3 program used 2, 4, 6, 9 then 12 mg.
Figures here use a 40 mg vial with 2 mL (20 mg/mL), so the 12 mg step is 0.6 mL.
Commonly reported reconstitution volumes are 1 mL (5-10 mg vials), 2 mL (20 and 40 mg), 2.5 mL (50 mg) and 3 mL (30 and 60 mg).