Retatrutide Reconstitution Calculator (mg → units)
A 10 mg vial of Retatrutide mixed with 2 mL of bacteriostatic water holds 5,000 mcg/mL, so a 4 mg dose is 0.8 mL — 80 units on a U-100 insulin syringe. Change the vial, water or dose below, or read the chart for other mixes.
Retatrutide dilution chart: 4 mg in units
| Vial | + 1 mL water | + 2 mL water | + 3 mL water | Doses per vial |
|---|---|---|---|---|
| 5 mg | 80 U 0.8 mL · 5,000 mcg/mL | 160 U 1.6 mL · 2,500 mcg/mL over 1 mL — more than one syringe | 240 U 2.4 mL · 1,667 mcg/mL over 1 mL — more than one syringe | 1.3 |
| 10 mg | 40 U 0.4 mL · 10,000 mcg/mL | 80 U 0.8 mL · 5,000 mcg/mL | 120 U 1.2 mL · 3,333 mcg/mL over 1 mL — more than one syringe | 2.5 |
| 20 mg | 20 U 0.2 mL · 20,000 mcg/mL | 40 U 0.4 mL · 10,000 mcg/mL | 60 U 0.6 mL · 6,667 mcg/mL | 5 |
1 mL = 100 units on a U-100 syringe. Water volume changes the units per dose, never the number of doses in the vial.
Retatrutide trial doses in units (20 mg vial + 2 mL)
| Dose | Units (U-100) | Volume | Context |
|---|---|---|---|
| 1 mg | 10 U | 0.1 mL | Lowest Phase 2 arm |
| 4 mg | 40 U | 0.4 mL | Phase 2 arm |
| 8 mg | 80 U | 0.8 mL | Phase 2 arm |
| 12 mg | 120 Uover 1 mL | 1.2 mL | Highest Phase 2 arm |
Mix: 20 mg vial + 2 mL water = 10,000 mcg/mL. Doses are the Phase 2 trial arms listed on our retatrutide page, shown only to illustrate the math. At this concentration 12 mg needs more than one 1 mL syringe.
Measuring Retatrutide: the math that matters
Retatrutide is dosed weekly in whole milligrams, and the trial arms span 1 mg to 12 mg. That twelvefold range is the measuring problem: a mix that makes 1 mg easy to see can make 12 mg impossible to fit in one syringe. With a 10 mg vial and 2 mL of bacteriostatic water the solution is 5,000 mcg/mL, so 4 mg is 0.8 mL, or 80 units on a U-100 syringe, and the vial holds two and a half doses.
Higher concentrations keep large doses inside one draw. A 20 mg vial with 2 mL is 10,000 mcg/mL: 1 mg is 10 units, 4 mg is 40, 8 mg is 80, and 12 mg is 120, which still spills past a 100-unit syringe. The same 20 mg vial with 1 mL would bring 12 mg to 60 units, at the cost of a smaller, harder-to-read 1 mg draw of 5 units.
Small vials run out quickly at these doses. A 5 mg vial holds one 4 mg dose with a remainder, and with 2 mL that one dose is already 160 units. When the chart shows a cell over 100 units, either the concentration is too low for that dose or the vial is too small for it.
The label on a grey-market vial is the least certain number in this calculation. Retatrutide sold outside clinical trials is an unregulated research chemical, and independent testing of similar products has found wrong sequences and contamination. The arithmetic here assumes the vial contains what it says.
Common Retatrutide measuring mistakes
- Picking the water volume for the lowest dose and then trying to draw 8 or 12 mg from the same dilute vial.
- Assuming "4" means units. At 10,000 mcg/mL, 4 units is only 0.4 mg.
- Splitting one dose across two syringes and losing track of how much went in the first.
- Using the Phase 2 dose list as if it were an approved schedule. Trial arms were fixed groups with their own escalation, not a ladder to climb.
- Mixing a new vial at a different volume from the last one and reusing last week's unit count.