How to Reconstitute Retatrutide (Dose and Units)

Retatrutide ships as a freeze-dried (lyophilized) powder. Before you can measure a single unit, the vial has to be reconstituted, which means adding bacteriostatic water to dissolve the powder into a liquid of known strength. This is a neutral lab-handling reference for a research compound, not medical guidance. It covers the mixing steps, a vial-size reconstitution table, and how the resulting concentration converts into units on an insulin syringe.

The one idea that anchors everything: the milligrams in the vial never change. Water does not add or remove peptide. It only sets the concentration, which decides how many units you draw for a given dose. To skip the arithmetic and run your own vial against any dose, the retatrutide calculator takes vial mg, water volume, and target dose and returns the draw directly.

What you need on hand

• The retatrutide vial. 10 mg is the common reference size; 5 mg and 20 mg also appear
• Bacteriostatic water, the standard diluent. See bacteriostatic water vs sterile water for why the bacteriostatic version suits multi-draw vials
• A larger syringe to transfer the water, plus U-100 insulin syringes for later draws
• Alcohol swabs and a clean, flat surface

The mixing steps

1. Let the vial and the water reach room temperature, then swab both rubber stoppers with alcohol.
2. Draw your chosen volume of bacteriostatic water into the transfer syringe (amounts in the table below).
3. Insert the needle at an angle and let the water run slowly down the inner glass wall, not straight onto the powder.
4. Do not shake. Swirl gently or let it sit until the solution turns clear. Shaking can stress the peptide. See swirl vs shake peptides.
5. Store the reconstituted vial in the refrigerator. See how to store peptides for handling after mixing.

Reconstitution table by vial size

There is no single correct water volume. It is a choice that sets your concentration, where concentration is total mg divided by total mL. These are common, easy-to-read pairings for each vial size.

5 mg vial:

• 1 mL water gives 5 mg/mL
• 0.5 mL water gives 10 mg/mL
• 2 mL water gives 2.5 mg/mL

10 mg vial (most common):

• 1 mL water gives 10 mg/mL
• 2 mL water gives 5 mg/mL
• 0.5 mL water gives 20 mg/mL

20 mg vial:

• 1 mL water gives 20 mg/mL
• 2 mL water gives 10 mg/mL
• 4 mL water gives 5 mg/mL

Turning concentration into units

On a U-100 insulin syringe, 100 units equals 1 mL, so 1 unit equals 0.01 mL. The reference formula is: units = (dose in mg divided by concentration in mg/mL) times 100. Two short examples on the common 10 mg vial in 1 mL (10 mg/mL):

• A 2 mg figure: (2 / 10) x 100 = 0.2 mL = 20 units
• A 4 mg figure: (4 / 10) x 100 = 0.4 mL = 40 units

Same vial, same water, the units just scale with the dose. Drop the same numbers into the retatrutide calculator and it returns the exact units and the line to fill to. For the method across any compound, the reconstitution calculator and mg to units calculator cover the same math.

Why the units differ between people

Two researchers can target the same milligram dose and read different units, because units depend on concentration, and concentration depends on how much water went into the vial. A 10 mg vial in 1 mL reads a 2 mg figure as 20 units; the same vial in 2 mL reads it as 40 units. Pin down vial strength and water volume first, then convert. For dose-step structure rather than mixing, see the retatrutide dosing guide.

• Same dose, more water means more units (lower concentration)
• Same dose, less water means fewer units (higher concentration)
• Switching to a new vial size resets the math, so recompute from the new strength

Retatrutide is a research compound and is not approved for human consumption. Any decision about whether or how much to use belongs with a licensed clinician. Read the full disclaimer.