Peptide Reconstitution Calculator
Mix a peptide vial with bacteriostatic water and find the units to draw for a dose in mcg or mg on a U-100 insulin syringe.
Updated · By Niraj Kumar · 3 sources
https://checkpre.com/health/peptide-reconstitution-calculator
Medication
Vial strength
The total mg on the vial.
Your dose
Exactly as written on your prescription. 1 mg is 1,000 mcg.
- Dose
- 0.25 mg
- 250 mcg
- Concentration
- 2.5 mg/mL
- Exact volume
- 0.1 mL
- 10 units (1 unit = 0.01 mL on a U-100 syringe)
- Doses in the vial
- 20
- 20 weeks at one dose a week. Most multi-dose vials must be discarded 28 days after first use; check yours.
How do you reconstitute a peptide and work out the units?
Divide the vial's mg by the mL of bacteriostatic water to get mg/mL. Then divide your dose in mg by that and multiply by 100 for units on a U-100 syringe. With mcg, divide by 1,000 first: 250 mcg from a 5 mg vial mixed with 2 mL is 10 units.
units = dose (mg) ÷ concentration (mg/mL) × 100This page uses the same method as the GLP-1 Dosage Calculator, which explains each term and assumption in full.
| Water added | Concentration | Units per dose |
|---|---|---|
| 1 mL | 5 mg/mL | 5 units |
| 1.5 mL | 3.333 mg/mL | 7.5 units |
| 2 mL | 2.5 mg/mL | 10 units |
| 2.5 mL | 2 mg/mL | 12.5 units |
| 3 mL | 1.667 mg/mL | 15 units |
Worked example
A 0.25 mg dose from a 5 mg vial mixed with 2 mL of bacteriostatic water.
- 1Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL
- 2Volume: 0.25 mg ÷ 2.5 mg/mL = 0.1 mL
- 3Units: 0.1 mL × 100 = 10 units
- 4Doses per vial: 5 mg ÷ 0.25 mg = 20
Draw to the 10 units line, on a 0.3 mL (30 units) U-100 insulin syringe.
Frequently asked questions
How do I convert mcg to units?
Divide the mcg by 1,000 to get mg, divide that by the vial's mg/mL, and multiply by 100. 500 mcg is 0.5 mg; from a 2.5 mg/mL vial that is 0.2 mL, or 20 units. Mixing up mcg and mg is a thousandfold error, so the calculator flags doses that look like the wrong unit.
Does adding more water change the dose?
No, only the volume it comes in. More water makes each unit weaker, so the same dose takes more units to draw. That is useful for small doses, which are easier to measure at 10 to 20 units than at 2 or 3. Only change how you mix a prescribed medicine on your pharmacy's instructions.
Sources
Related calculators
- Bacteriostatic Water CalculatorHow much bacteriostatic water to add to a vial so each dose lands on an easy line, like 10 or 20 units, on a U-100 syringe.
- GLP-1 Dosage CalculatorTurn a prescribed semaglutide or tirzepatide dose in mg into the exact line on a U-100 insulin syringe, with the syringe drawn to scale.
- Insulin Syringe Units to mg CalculatorWork backwards from the line on a U-100 insulin syringe to the dose in mg or mcg, for any vial strength.
- Semaglutide Dosage CalculatorCompounded semaglutide in mg to units on an insulin syringe, for any vial strength, with the Wegovy titration converted for your vial.