Reconstitution and syringe units
Retatrutide Calculator
Convert a retatrutide vial, the water added and a dose into exact units on a U-100 insulin syringe.
Retatrutide reconstitution calculator
Example values are loaded. Replace them with the numbers on your own vial.
Retatrutide is not FDA-approved. It is an investigational medicine from Eli Lilly (development code LY3437943) still in clinical trials. Products sold online as "research" retatrutide are not the trial drug, are not approved for human use, and their contents are not verified.
What retatrutide is
Retatrutide is a once-weekly injectable that acts on three hormone receptors: GIP, GLP-1 and glucagon. That is one more than tirzepatide (GIP and GLP-1) and two more than semaglutide (GLP-1 only). Lilly announced the first phase 3 result, from the TRIUMPH-4 trial, in December 2025: participants on the highest dose lost an average of 28.7% of body weight over 68 weeks, against 2.1% on placebo. More phase 3 readouts followed in 2026.
In the trials, retatrutide comes in pre-filled form. Reconstitution math matters only for lyophilized vials, which is also where the arithmetic mistakes happen.
Units chart: 10 mg vial with 1 mL water
At 10 mg/mL, each unit on a U-100 syringe holds 0.1 mg. The dose levels below are the ones studied in published trials (phase 3 tested 9 mg and 12 mg as top doses).
| Dose | Units (U-100) | mL |
|---|---|---|
| 1 mg | 10 | 0.1 |
| 2 mg | 20 | 0.2 |
| 4 mg | 40 | 0.4 |
| 6 mg | 60 | 0.6 |
| 8 mg | 80 | 0.8 |
| 9 mg | 90 | 0.9 |
| 12 mg | 120 | 1.2 |
Units chart: 10 mg vial with 2 mL water
Doubling the water halves the concentration to 5 mg/mL, so every draw doubles in units. Values over 100 do not fit a 1 mL syringe in one draw.
| Dose | Units (U-100) | mL |
|---|---|---|
| 1 mg | 20 | 0.2 |
| 2 mg | 40 | 0.4 |
| 4 mg | 80 | 0.8 |
| 6 mg | 120 | 1.2 |
| 8 mg | 160 | 1.6 |
| 9 mg | 180 | 1.8 |
| 12 mg | 240 | 2.4 |
Larger vials
Vials above 10 mg are more concentrated at the same water volume. A 30 mg vial with 3 mL of water is also 10 mg/mL, so the first chart above applies to it too. What changes is the number of doses in the vial and how long it takes to use, which matters because a punctured vial has a limited use window. The vial supply calculator shows how long a vial lasts on a given schedule.
Frequently asked questions
How many units is 2 mg of retatrutide?
It depends on the concentration. In a 10 mg vial with 1 mL of water (10 mg/mL), 2 mg is 20 units. With 2 mL of water (5 mg/mL), it is 40 units.
How much water do I add to a 10 mg retatrutide vial?
The water volume only sets the concentration. 1 mL gives 10 mg/mL; 2 mL gives 5 mg/mL. The BAC water calculator finds the volume that makes your dose a round number of units.
Is retatrutide approved?
No. As of September 2026, retatrutide is investigational and not approved by the FDA.