How the calculation works
Reconstitution is three steps of simple division. First, find the concentration of the mixed vial:
concentration (mg/mL) = peptide in vial (mg) ÷ water added (mL)
Then find the volume that holds your dose, and turn it into syringe units (on a U-100 syringe, 1 mL = 100 units):
volume (mL) = dose (mg) ÷ concentration
units = volume (mL) × 100
Worked example
A 10 mg vial mixed with 2 mL of bacteriostatic water is 5 mg/mL. A dose of 250 mcg (0.25 mg) is 0.25 ÷ 5 = 0.05 mL, which is 5 units. The vial holds 10 ÷ 0.25 = 40 doses.
Getting a dose you can actually measure
- Aim for a whole number of units, ideally 10 or more. Below about 5 units, small reading errors become a big share of the dose.
- If your dose comes out awkward, change the water, not the dose. The BAC water calculator finds the amount that lands your dose on a clean mark.
- Use the smallest syringe that holds your dose: a 0.3 mL syringe has finer markings than a 1 mL one.
- Mixing two or more peptides in one vial? Use the blend calculator.
Questions
How many units is 250 mcg?
It depends on how much water you added. In a 10 mg vial mixed with 2 mL of water (5 mg/mL), 250 mcg is 0.05 mL, which is 5 units on a U-100 syringe. Mixed with 1 mL instead, the same 250 mcg is 2.5 units.
Does adding more water change the dose?
No. The vial holds the same amount of peptide whatever you add. More water only makes each unit weaker, so you draw more units for the same dose. That can make small doses easier to measure.
What is a U-100 insulin syringe?
The standard insulin syringe in the US. U-100 means 100 units fill 1 mL, so 1 unit is 0.01 mL. They come in 0.3 mL (30 units), 0.5 mL (50 units) and 1 mL (100 units) sizes; smaller barrels have finer markings.
How many doses are in my vial?
Divide the peptide in the vial by your dose. A 10 mg vial at 250 mcg per dose holds 40 doses. The calculator shows this as “Doses per vial”; in practice you lose a little to the needle and the vial, so plan for slightly fewer.
Is this calculator medical advice?
No. It only does the arithmetic from the numbers you enter. It doesn't tell you what dose to take. Check every result against your vial label, and talk to a licensed clinician about dosing.