Peptide Reconstitution Calculator
To reconstitute a peptide vial, divide the vial strength in milligrams by the millilitres of bacteriostatic water you add. That gives the concentration in mg/mL. To find the syringe units for a given dose, divide the dose by the concentration to get the volume in millilitres, then multiply by 100 for a U-100 insulin syringe.
The formula
units = (dose mg ÷ (vial mg ÷ BAC water mL)) × 100
The inner division gives the concentration in mg per mL. Dividing the dose by that concentration gives the volume in millilitres. Multiplying by 100 converts millilitres to units on a U-100 insulin syringe, where 100 units equals 1 mL.
Convert a dose to syringe units
Enter your vial and dose to see the units to draw.
Example values are prefilled. Replace them with your own.
- Concentration
- 2.5 mg/mL
- Volume to draw
- 0.1 mL
- Per unit
- 25 mcg
- Doses per vial
- 20
Peptio for iOS & Android
Keep a record of every dose
Track one medication at a time, including a custom peptide. Log your doses and injection sites, set reminders, and look back at your history in Peptio.
Free to download. Optional paid features in the app.
Worked examples
Common vial and bacteriostatic water pairings, with the resulting concentration and units to draw.
5 mg vial, 2 mL water
10units
- Concentration
- 2.5 mg/mL
- Dose
- 0.25 mg
- Volume
- 0.1 mL
10 mg vial, 2 mL water
20units
- Concentration
- 5 mg/mL
- Dose
- 1 mg
- Volume
- 0.2 mL
15 mg vial, 3 mL water
50units
- Concentration
- 5 mg/mL
- Dose
- 2.5 mg
- Volume
- 0.5 mL
30 mg vial, 3 mL water
25units
- Concentration
- 10 mg/mL
- Dose
- 2.5 mg
- Volume
- 0.25 mL
Frequently asked questions
- How much bacteriostatic water do I add to a 10 mg vial?
- Any volume works arithmetically — it changes the concentration, not the total peptide in the vial. Adding 1 mL to a 10 mg vial gives 10 mg/mL, and 2 mL gives 5 mg/mL. More water means more syringe units for the same dose, which makes small doses easier to measure accurately. Your supplier's or prescriber's instructions take precedence.
- How many units is 0.25 mg?
- It depends entirely on the concentration. At 2.5 mg/mL (a 5 mg vial in 2 mL of water), 0.25 mg is 0.1 mL, which is 10 units on a U-100 syringe. At 5 mg/mL, the same 0.25 mg is only 5 units.
- What does U-100 mean on an insulin syringe?
- U-100 means the syringe is marked at 100 units per millilitre, so 100 units is 1 mL and 10 units is 0.1 mL. Units are a volume marking, not a measure of mass — the milligrams they represent depend on your concentration.
- Does adding more bacteriostatic water reduce the dose?
- No. It dilutes the peptide, so the same dose occupies a larger volume and more syringe units, but the milligrams delivered are unchanged if you draw the correct number of units.
- How do I reconstitute a 30 mg vial?
- Adding 3 mL of bacteriostatic water to a 30 mg vial gives 10 mg/mL. A 2.5 mg dose is then 0.25 mL, or 25 units on a U-100 syringe.