Peptide & GLP-1 Reconstitution Calculator
Reconstituting a peptide or compounded GLP-1 means turning dry powder into an injectable solution. Enter your vial strength, the bacteriostatic water you add, and the dose you want, and this tool returns the concentration, the volume to draw, and the exact units on a U-100 insulin syringe.
The total milligrams of peptide in the dry vial, from the label.
How much water you draw into the vial to reconstitute it.
The single dose you want to draw. This tool does the math only, it does not set your dose.
Draw this much
Insulin syringe units (U-100)
10units
The mark to draw to on a standard U-100 insulin syringe. Confirm the scale on your own syringe.
Volume per dose
0.1mL
How this works
The math is short. Your concentration is the milligrams of peptide in the vial divided by the millilitres of bacteriostatic water you added:
concentration (mg/mL) = peptide mg / water mL
To draw a dose, divide the dose by that concentration to get a volume in millilitres, then multiply by 100 to read it as units on a standard U-100 insulin syringe (where 100 units equal 1 mL):
volume (mL) = dose mg / concentration
units (U-100) = volume mL x 100
Doses per vial is simply the vial strength divided by your dose, rounded down to whole doses. If you enter your dose in micrograms, the tool converts it to milligrams first (1 mg = 1000 mcg).
This is arithmetic on numbers you provide, not a recommendation. Your prescriber and pharmacist set your dose, concentration, and how to prepare the vial. For tracking compounded supplies over time, see tracking compounded semaglutide and tirzepatide.
Frequently asked questions
How do I work out the concentration after reconstitution?
Concentration equals the milligrams of peptide in the vial divided by the millilitres of bacteriostatic water you added. For example, 5 mg of peptide in 2 mL of water gives 2.5 mg/mL.
How do insulin syringe units relate to millilitres?
This tool assumes a standard U-100 insulin syringe, where 100 units equal 1 mL. So a 0.2 mL draw is 20 units. Always read the units printed on your own syringe.
Is this telling me how much to inject?
No. It only does the arithmetic for numbers you enter. Your prescriber and pharmacist decide your actual dose, concentration, and schedule. Verify every figure with them before drawing anything.
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