How it works
This runs the reconstitution maths backwards. You decide how much liquid each dose should be, and the water follows from that:
volume per dose (mL) = units ÷ 100
concentration needed (mg/mL) = dose (mg) ÷ volume per dose
water to add (mL) = peptide in vial (mg) ÷ concentration needed
1 mL, 2 mL or 3 mL of bac water: what does each give?
1 mL of bacteriostatic water is 100 units on a U-100 syringe, 2 mL is 200 units and 3 mL is 300 units. Here is what a 10 mg vial looks like with each amount:
| Water added | Liquid in the vial | Strength | mg in 10 units | Units for 1 mg |
|---|---|---|---|---|
| 1 mL | 100 units | 10 mg/mL | 1 mg | 10 units |
| 2 mL | 200 units | 5 mg/mL | 0.5 mg | 20 units |
| 3 mL | 300 units | 3.33 mg/mL | 0.33 mg | 30 units |
10 mg vial, U-100 syringe. The same maths works for any vial size: strength = vial mg ÷ water mL.
Worked example
You have a 10 mg vial and want each 250 mcg dose to be 10 units (0.1 mL). The concentration needs to be 0.25 ÷ 0.1 = 2.5 mg/mL, so you add 10 ÷ 2.5 = 4 mL of water. If 4 mL is more than you want in the vial, pick 5 units instead and you need 2 mL.
Choosing a good amount
- Whole-number doses between 10 and 50 units are the easiest to read accurately.
- Keep the total within what your vial holds comfortably, usually 3 to 5 mL at most.
- Add the water slowly down the inside wall of the vial and swirl gently; don’t shake.
- Already mixed your vial? Use the peptide calculator to find your units, or the units to mg converter for a full chart.
Questions
1 ml of bac water is how many units?
100 units. A U-100 insulin syringe holds 100 units in 1 mL, so 1 mL of bacteriostatic water is 100 units of liquid, 2 mL is 200 units and 3 mL is 300 units. What changes with the amount of water is how much peptide sits in each unit, not the 100 units per mL.
How much BAC water do I add to a 10 mg vial?
There is no single right amount; it depends on the dose you want to measure. 1 to 3 mL is typical. At 2 mL, a 10 mg vial is 5 mg/mL, so every 10 units holds 500 mcg. If your doses are small, more water makes them easier to measure; if they are large, less water keeps each draw inside one syringe.
How much bac water for 5 mg of peptide?
With 1 mL, 5 mg is 5 mg/mL (50 mcg per unit). With 2 mL it is 2.5 mg/mL (25 mcg per unit). Enter your dose above and the units you want, and the calculator gives the exact amount.
Does more water make the peptide weaker?
Each unit gets weaker, but the vial holds the same total peptide, so your dose is the same; you simply draw more units for it. The amount of water changes how easy the dose is to measure, not how much you get.
What is bacteriostatic water?
Sterile water with 0.9% benzyl alcohol added as a preservative, which stops bacteria growing when a vial is used more than once. Sterile water without the preservative is meant for single use.
What if the answer is more than my vial can hold?
Most peptide vials hold about 3 to 5 mL comfortably. If the result is higher, choose a larger number of units per dose, which needs less water.