How to Reconstitute Retatrutide (Step by Step)

By DoseGauge Editorial · Updated 2026-06-12 · 5 min read

Reconstituting retatrutide means adding bacteriostatic water to the lyophilized (freeze-dried) powder in the vial until it dissolves into an injectable solution. The volume of water you add sets the concentration in milligrams per milliliter, and that concentration is what turns a milligram dose into a number of units on a syringe. The calculator on this site does that conversion from your inputs. Retatrutide is investigational and not FDA-approved as of June 2026, so handle it as a research compound and follow the storage guidance from your supplier.

What you need

• A vial of lyophilized retatrutide (commonly labeled 10, 20, 30, or 60 mg).
• Bacteriostatic water for injection. This is sterile water with about 0.9% benzyl alcohol added as a preservative, which is why it suits multi-dose vials that you draw from over several days. For the full definition, see what is bacteriostatic water.
• A U-100 insulin syringe for drawing doses, plus a larger syringe (for example 1 to 3 mL) for adding the water.
• Alcohol wipes for the vial stoppers.

Bacteriostatic water is the usual reconstitution fluid here because the preservative lets you withdraw repeated doses from one vial. Its FDA label notes it is for diluting or dissolving drugs and carries a warning against use in neonates due to the benzyl alcohol.

Step by step

1. Wipe the stopper of both the retatrutide vial and the bacteriostatic water vial with an alcohol swab and let them dry.
2. Draw your chosen volume of bacteriostatic water into the larger syringe. The volume you pick sets the concentration, so decide it before you start (the math is below).
3. Insert the needle into the retatrutide vial and angle it so the water runs slowly down the inside glass wall, not directly onto the powder. Release the water gently.
4. Remove the needle. Swirl the vial slowly to dissolve the powder. Do not shake it, since agitation can stress the peptide and create foam.
5. Let it sit until the solution is clear. Once dissolved, store it as below and draw doses with a U-100 syringe.

The reconstitution math

The conversion from milligrams to syringe units is arithmetic, driven entirely by how much water you added:

concentration (mg/mL) = vial strength (mg) / water added (mL)
draw volume (mL)       = dose (mg) / concentration (mg/mL)
units (U-100 syringe)  = draw volume (mL) x 100

Worked example. Reconstitute a 10 mg retatrutide vial with 1 mL of bacteriostatic water and the concentration is 10 mg/mL. A 2 mg dose is then 2 / 10 = 0.20 mL, which is 20 units on a U-100 insulin syringe, and the vial holds 5 such 2 mg amounts. Add 2 mL instead and the concentration becomes 5 mg/mL, so the same 2 mg dose is 0.40 mL, or 40 units. The dose in milligrams did not change; the units did, because the concentration did.

This is why a units figure copied from someone else is unreliable unless their vial and water volume match yours exactly. Enter your own numbers and the calculator returns the draw volume and units, and flags whether the dose fits one U-100 syringe. For the formulas and how the engine computes them, see the methodology page.

Storage and handling

Store the reconstituted vial refrigerated, typically around 2 to 8 degrees Celsius, and keep it out of light. Bacteriostatic water's preservative is what allows multi-dose use over a period of days to weeks, but the usable window depends on the specific product, so follow the storage period your supplier specifies rather than assuming a fixed number. Inspect the solution before each draw and do not use it if it is cloudy or contains particles. Because retatrutide is investigational, there is no FDA-approved stability or storage labeling for the finished product to fall back on.

Frequently asked questions

How much bacteriostatic water do I add to retatrutide?

There is no single correct volume. The amount of water sets the concentration, and the concentration determines the units you draw. A 10 mg vial in 1 mL gives 10 mg/mL; the same vial in 2 mL gives 5 mg/mL. Pick a volume, then use the calculator to see the resulting units for your dose, or work backward from a concentration you find easy to measure.

Can you shake the retatrutide vial?

No. Swirl it gently instead. Shaking agitates the peptide and can cause foaming, which makes the solution harder to draw accurately. Let it dissolve on its own after a slow swirl.

What syringe do you use for retatrutide?

A U-100 insulin syringe for drawing doses, because its scale reads directly in units (1 mL equals 100 units). A larger syringe is handy for adding the bacteriostatic water during reconstitution. The calculator reports the draw in both milliliters and units.

How long does reconstituted retatrutide last?

That depends on the product and your supplier's guidance, not on a universal number. Bacteriostatic water's preservative supports multi-dose use over days to weeks when refrigerated, but retatrutide is investigational with no FDA stability labeling, so follow the storage period your supplier specifies and discard if the solution looks off.

Informational and educational only. Not medical advice. DoseGauge computes from the values you enter and does not recommend a dose. Talk to a licensed clinician before using any peptide or GLP-1 medication.