How to reconstitute a vial

What you need

• The sealed vial of freeze-dried powder.
• Bacteriostatic water, the multi-dose kind, with a preservative that supports repeated draws over about 28 days.
• A U-100 insulin syringe for drawing doses, and a larger syringe for adding the water.
• Alcohol swabs.

The steps

1. Let both vials reach room temperature and swab both rubber stoppers with alcohol.
2. Draw your chosen volume of bacteriostatic water into the larger syringe.
3. Insert the needle at an angle and let the water run slowly down the inside wall of the vial, not directly onto the powder.
4. Remove the syringe. Gently swirl or roll the vial until the powder fully dissolves. Do not shake.
5. Let it settle. The solution should be clear. Draw your measured dose with the U-100 syringe.

How much water should you add?

There is no single right answer. The water volume is a choice that sets your concentration, and therefore how many units you draw per dose. Less water makes a stronger solution (fewer units per dose); more water makes it more dilute (more units, easier to read on the syringe).

A common approach is to pick a water amount that lands your usual dose on an easy round number of units. The calculator does this instantly: enter the vial amount and your dose, then try different water volumes and watch the units update.

Why swirl instead of shake

Vigorous shaking forces air into the solution and can create foam and mechanical stress. Gentle swirling or rolling dissolves the powder without either. Give it a minute; if a little material remains, swirl again rather than shaking.