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Guide
Reconstitution math comes down to three short formulas: concentration from your vial and water, the volume for a dose, and the syringe units to draw. This guide states each formula, works an example, and links the calculators that do it for you. Reference only, not medical advice.
Concentration = vial mg / water mL
The concentration of your solution is the peptide mass in the vial divided by the bacteriostatic water you add. A 10 mg vial reconstituted with 2 mL of water gives 10 / 2 = 5 mg/mL. Adding more water lowers the concentration; adding less raises it.
Dose volume = dose / concentration
To find how much liquid a dose is, divide the dose by the concentration. At 5 mg/mL, a 0.5 mg dose is 0.5 / 5 = 0.1 mL. This is the volume you draw into the syringe, in milliliters.
Units = volume x 100 (U-100)
On a U-100 insulin syringe there are 100 units per milliliter, so multiply the dose volume in mL by 100 to get units. The 0.1 mL example above is 10 units. Putting it together: 0.5 mg at 5 mg/mL is 0.1 mL, which is 10 units to draw.
Frequently asked questions
What is the reconstitution formula?
Concentration equals vial mg divided by water mL. Dose volume equals dose divided by concentration. Units to draw equals dose volume times 100 on a U-100 syringe. Those three steps take you from a vial to the units on the syringe.
How do I calculate concentration?
Divide the milligrams of peptide in the vial by the milliliters of bacteriostatic water you add. For example, a 5 mg vial with 2 mL of water is 2.5 mg/mL. The bacteriostatic water calculator does this both ways.
How do I turn a dose into units?
Divide the dose by the concentration to get milliliters, then multiply by 100 for a U-100 syringe. For example, 0.25 mg at 2.5 mg/mL is 0.1 mL, or 10 units. The mg-to-units converter and insulin syringe calculator handle it.
Does the water volume change my dose?
No. The water sets the concentration and therefore how many units a dose measures, but the milligrams you draw for a given dose stay the same. Use the reconstitution solver to pick a water volume that lands your dose on a round number of units.
Is this medical advice?
No. These are arithmetic relationships provided for reference. They do not recommend a dose or a concentration. Verify with the product label and a clinician or pharmacist.