Retatrutide Reconstitution Calculator

Retatrutide reconstitution chart for 10 mg and 20 mg vials

The table runs the calculator arithmetic for 10 mg and 20 mg retatrutide (often shortened to reta) vials at 1, 2 and 3 mL of bacteriostatic water. Units are on a U-100 insulin syringe, where 1 unit is 0.01 mL.⁴

Disclaimer: these are unit conversions, not dose recommendations. Educational only; dose decisions belong with a licensed clinician.

How retatrutide reconstitution works

Retatrutide is a triple hormone-receptor agonist studied for obesity in a published Phase 2 trial.¹ It ships as a freeze-dried (lyophilized) powder, which has to be dissolved in liquid before any dose can be measured.⁵ Reconstitution is that mixing step: you add a known volume of bacteriostatic water to the vial,² which turns the powder into a solution at a known concentration. That concentration is what lets a dose be drawn accurately.

The arithmetic has three steps, and the calculator above runs all three as you type:

The last step uses the U-100 insulin syringe conversion, where 1 unit equals 0.01 mL.⁴ The amount of water you add changes the concentration and the volume you draw, never the total milligrams of peptide in the vial.

Why 2 mL is the default

This calculator pre-fills 2 mL of bacteriostatic water, and there is a safety reason behind that number. 2 mL fits comfortably inside common research vial sizes, so it never asks you to add a volume the vial physically cannot hold. A calculator that suggested, say, 5 mL for a 3 mL vial would produce unit counts that look authoritative but describe a mix you could never make, and that is exactly how a small measurement turns into a large error.

2 mL also keeps most draws in a range a U-100 syringe reads well, though a higher-strength vial gets concentrated, so the draw gets smaller. A 20 mg vial in 2 mL is 10 mg/mL, so a 0.5 mg amount is only 5 units. When any draw lands under about 5 units, the calculator flags it and tells you to draw slowly, because that is where a misread of one or two units matters most. It never silently rounds a small draw away.

The bacteriostatic water field stays free entry on purpose. 2 mL is the default, but you should enter the exact volume you actually mixed, and the concentration, units, and dose count will follow from your real number.

How to reconstitute a retatrutide vial

1. Swab both stoppers. Wipe the rubber stopper of the peptide vial and the bacteriostatic water vial with an alcohol swab and let them dry.
2. Draw the water. Draw the bacteriostatic water volume the calculator shows, 2 mL by default, into a syringe.
3. Inject down the wall. Insert the needle at a slight angle so the water runs down the inside wall of the vial rather than directly onto the powder. This reduces foaming.
4. Swirl, do not shake. Inject the water slowly. Do not shake the vial. Swirl gently until the solution is clear.
5. Label the vial. Label the vial with the reconstitution date and the concentration in mg per mL.
6. Refrigerate. Refrigerate the reconstituted vial. Do not freeze it. Follow the supplier storage instructions.

Research-grade retatrutide is supplied as a powder and taken into solution with a preserved diluent at the volume above. Our supply partner Peptara Labs sells bacteriostatic water in 3, 5 and 10 mL bottles. After reconstituting, keep the diluent and the mixed vial stored correctly: our guide to bacteriostatic water storage and shelf life lays out the room-temperature and refrigeration rules from the labels.

Worked examples

The amounts below are round numbers chosen to keep the arithmetic easy to follow. They are illustrations of the math, not doses to take. Use the figures your own protocol source specifies.

Disclaimer: this is educational only, individual protocols vary, and dose decisions belong with a licensed clinician.

Notice that the same 2 mL of water gives very different unit counts depending on the vial strength. That is why you enter your own vial size rather than copying a unit number from somewhere else.

Reading the insulin syringe

Reconstituted peptides are almost always drawn with a U-100 insulin syringe. The conversion is fixed:

So a 0.4 mL draw is 40 units, and a 0.05 mL draw is 5 units. The calculator shows both the millilitre volume and the unit count, and it checks the volume against the 0.3 mL, 0.5 mL, or 1.0 mL barrel you select. Smaller barrels have finer graduations and are easier to read for small draws.

How the water volume changes the draw

The volume of bacteriostatic water you add does not change how much peptide is in the vial. It changes the concentration, and with it the volume you draw for a given amount. A 10 mg vial reconstituted with 1 mL is twice as concentrated as the same vial with 2 mL, so the draw is half the liquid volume for the same amount.

If you want the same concentration math without a compound preset, the general peptide reconstitution calculator handles any vial, and the beginner injection guide walks through the mixing and measuring steps in plain terms.

Safety notes before you mix or draw

In the phase 2 obesity trial, the most common side effects of retatrutide were gastrointestinal, mostly mild to moderate, and they rose with the dose.¹ The same trial reported dose-dependent increases in heart rate that peaked at 24 weeks and then declined.¹ These are observations under trial monitoring, not a safety verdict for use outside a trial.

The FDA has reported adverse events, some requiring hospitalisation, from dosing errors with compounded semaglutide, a different GLP-1 drug, where people measured and injected the wrong amount.⁶ Before you draw, check that the dose and the vial are both in mg and that your syringe is U-100. If a result here looks surprising, stop and recheck it with your protocol source or a clinician.

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