This calculator answers the one question every reconstitution comes down to: how many units do I draw? Enter the milligrams of peptide in the vial, the volume of bacteriostatic water you added, and the dose you want in micrograms. It returns the mark to draw to on a standard insulin syringe, plus the resulting concentration.
The formula
Reconstitution is simple arithmetic once the units line up:
- Concentration (mcg/mL) = vial amount (mg) × 1000 ÷ water added (mL)
- Volume to inject (mL) = target dose (mcg) ÷ concentration (mcg/mL)
- Syringe units = volume (mL) × units-per-mL of your syringe (100 for U-100)
Example: 5 mg in 2 mL is 2500 mcg/mL. A 250 mcg dose is 0.1 mL — that is 10 units on a U-100 insulin syringe.
Why concentration matters more than the number
More water means a lower concentration and a larger, easier-to-measure volume — helpful for small doses. Less water means a higher concentration and less volume to inject. The peptide quantity is fixed; you are only choosing how to dilute it. This tool lets you try water volumes until the units land somewhere you can read precisely on your syringe.