Mixing calculator
How many units do I draw?
Enter what is in your vial and the dose your prescriber gave you. We do the math, show it on a syringe, and point out the water amount that makes your dose easiest to measure.
What’s in your vial?
Step 1Printed on the vial label, usually in mg.
Your prescribed dose
Step 2Use the exact dose from your prescriber or pharmacy label. 1 mg = 1,000 mcg. Example numbers are filled in so you can see how it works.
Your syringe
Step 3Standard U-100 insulin syringes: 100 units = 1 mL.
Water you add
Step 4Bacteriostatic water. Already mixed your vial? Enter what you actually added.
How it works
The math, step by step
- Find the concentration. Divide the peptide in the vial by the water you add.
10 mg ÷ 2 mL = 5 mg per mL - Match the units. Convert your dose to mg.
500 mcg = 0.5 mg - Find the volume. Divide your dose by the concentration.
0.5 mg ÷ 5 mg/mL = 0.1 mL - Convert to units. On a U-100 syringe, multiply mL by 100.
0.1 mL × 100 = 10 units
Tips for measuring accurately
- Pick a water amount that puts your dose on a whole-number line, and between about 10 and 50 units on a 100-unit syringe. Very small draws are hard to measure.
- More water does not weaken the vial. It spreads the same amount over more liquid, so you draw more units.
- Write the concentration and the date on the vial after mixing, so you never have to redo the math.
- Follow your pharmacy’s instructions for mixing, storage and how long the vial lasts once mixed.
- Double-check your numbers with your pharmacist the first time.
Common questions
How much bacteriostatic water should I add to my peptide vial?
Any amount works. The water only changes how concentrated the liquid is, not how much peptide is in the vial. Pick an amount that makes your prescribed dose easy to measure, ideally a whole number of units between about 10 and 50 on a 100-unit syringe. The calculator shows the easiest option for your numbers.
What does 1 unit mean on an insulin syringe?
On a standard U-100 insulin syringe, 100 units equals 1 mL, so 1 unit is 0.01 mL. A 30-unit syringe holds 0.3 mL and a 50-unit syringe holds 0.5 mL.
How do I convert mcg to units?
First work out the concentration: milligrams in the vial divided by milliliters of water. Convert your dose to milligrams (1,000 mcg = 1 mg), divide it by the concentration to get milliliters, then multiply by 100 to get units on a U-100 syringe.
How many doses are in my vial?
Divide the amount in the vial by your dose, using the same unit for both. A 10 mg vial holds 20 doses of 500 mcg. In practice you may get slightly fewer because a little liquid stays in the vial.
Does adding more water make a peptide weaker?
Each unit on the syringe holds less peptide, but the total in the vial stays the same. You just draw more units to get the same dose.
This calculator only converts your own numbers. It does not recommend peptides or doses, and it is not medical advice. Always use the dose and instructions from your prescriber or pharmacy, and confirm your math with a pharmacist. Last reviewed 2026-09-26.