Peptide reconstitution calculator.

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How reconstitution math works

Reconstitution is just figuring out a concentration, then a volume. When you add bacteriostatic (BAC) water to a lyophilised vial, you create a known concentration:

• Concentration = vial strength ÷ water added. A 10 mg vial with 2 mL of water is 5 mg/mL, i.e. 5000 mcg/mL.
• Volume to draw = target dose ÷ concentration. A 250 mcg dose at 5000 mcg/mL is 0.05 mL.
• Units to draw = volume × the syringe scale. On a U-100 syringe, 0.05 mL is 5 units.

The only common mistake is mixing up the syringe scale. U-100 is by far the most common insulin syringe — 100 units to the millilitre. U-40 syringes (40 units/mL) still exist; if you draw a U-100 dose on a U-40 barrel you'll be off by 2.5×.

Worked example

Say you have a 5 mg vial of a peptide, you add 2 mL of BAC water, and you want a 250 mcg dose on a U-100 syringe:

• Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL = 2500 mcg/mL
• Volume: 250 mcg ÷ 2500 mcg/mL = 0.1 mL
• Units: 0.1 mL × 100 = 10 units

Change the water you add and the units change — more water means a more dilute solution and more units per dose, which can make small doses easier to measure accurately.