Retatrutide Dose Calculator: Reconstitution and Syringe Units

1. Say whether the vial is already mixed. If it is, enter the mg printed on the vial and the mL of water you added; the calculator gives the concentration.
2. Enter the amount in mg you plan to draw and choose your syringe: 0.3 mL (30 units), 0.5 mL (50 units) or 1 mL (100 units). The calculator suggests no amount.
3. Read the units, the mL and how many of your amounts the vial holds.
4. If you have not mixed yet, the calculator lists the water volumes that put your amount on a round mark of your syringe, best first. Print a label for the vial with the mix date.

Concentration in mg/mL = powder in mg ÷ water in mL. Units = amount in mg ÷ concentration in mg/mL × 100, because 100 units on a U-100 syringe fill 1 mL (FDA alert on compounded semaglutide dosing errors).

The numbers in this example are arbitrary, picked to keep the division easy, and none of them is a dose. A vial labeled 10 mg mixed with 2 mL of water is 10 ÷ 2 = 5 mg/mL. Each unit mark then holds 5 ÷ 100 = 0.05 mg, and each mg takes 1 ÷ 5 × 100 = 20 units, or 0.2 mL.

The same 10 mg vial gives a different concentration for each volume of water, and the amount in every unit mark moves with it.

From the same vial, 20 units of the 1 mL mix carry twice as much drug as 20 units of the 2 mL mix. A unit count copied from someone else cannot be turned into mg without the water volume they used, so write the volume on the vial when you mix it.

More water means each mark holds less, 0.05 mg at 5 mg/mL against 0.2 mg at 20 mg/mL, and more liquid to inject for the same amount. The calculator warns when an amount needs more than the syringe you chose holds.

Every result assumes the vial holds what its label says. Lilly warns that illicit retatrutide may contain "too much or too little active ingredient, or the wrong ingredient entirely" (Lilly, what to know about retatrutide).

Retatrutide has no approved label, so there is no starting dose, step schedule, maximum or missed-dose rule to check a result against. Lilly says it is legally available only through Lilly’s clinical trials and that anything sold to consumers outside them is illegal (Lilly, what to know about retatrutide). FDA says retatrutide cannot be used in compounding under federal law and has "not been found safe and effective for any condition" (FDA, concerns with unapproved GLP‑1 drugs). The trial results, the approval timeline and what "research use only" on a vial means are in what retatrutide is and where its trials stand.

For contrast, the Zepbound label gives a 2.5 mg starting dose for 4 weeks, 2.5 mg steps after at least 4 weeks, a 15 mg maximum, a 4-day (96-hour) window for a missed dose and a fixed volume for each pen and vial (Zepbound prescribing information, sections 2 and 3). The Ozempic label sets a 0.25 mg start and a 2 mg maximum (Ozempic prescribing information, section 2.2). Every approved ladder is in the GLP‑1 dose conversion chart, and the reverse dose calculator turns units back into mg for any vial.