Peptide Reconstitution Calculator.
Convert your vial mass, bacteriostatic water volume, and target dose into the exact number of units to draw on an insulin syringe.
Medical Disclaimer
This calculator is provided for educational reference only. It is not a substitute for professional medical advice. Confirm every reconstitution ratio and dose with your prescribing clinician or compounding pharmacist before injection.
How the Math Works
Reconstitution is just a chain of unit conversions. Start with the dry powder, dilute it with a known volume of bacteriostatic water, then back-solve for the volume that contains your target dose.
- 01Concentration. Divide vial mass (mg) by water volume (mL). A 5 mg vial in 2 mL of bacteriostatic water yields a 2.5 mg/mL solution.
- 02Unit scale. Multiply concentration by 1000 to convert to micrograms per mL (2.5 mg/mL = 2500 μg/mL). Most peptides are dosed at the microgram level, so this keeps the math clean.
- 03Injection volume. Divide target dose (μg) by concentration (μg/mL). A 250 μg dose at 2500 μg/mL needs 0.10 mL.
- 04Syringe units. Multiply mL by the syringe scale. On a U-100 syringe, 0.10 mL = 10 units. On a U-40 syringe, the same 0.10 mL would read as 4 units — which is why the syringe type matters.
- 05Doses per vial. Total vial μg divided by per-dose μg. 5000 μg / 250 μg = 20 doses.
Worked Example
Frequently Asked Questions
What does it mean to reconstitute a peptide?+
Reconstitution is the process of mixing a freeze-dried (lyophilized) peptide powder with bacteriostatic water so it can be drawn into a syringe and injected. The dry peptide is shipped that way because most peptides degrade in solution.
How is the dose in units calculated?+
First, the calculator divides the vial mass (mg) by the volume of bacteriostatic water (mL) to find concentration. It then divides the target dose (μg) by that concentration to find the injection volume in mL, and finally converts mL to syringe units (100 units = 1.0 mL on a U-100 syringe; 40 units = 1.0 mL on a U-40).
What is the difference between a U-100 and a U-40 syringe?+
A U-100 syringe is calibrated so 100 units equals 1.0 mL — the standard for most insulin and research peptides. A U-40 syringe (40 units per 1.0 mL) is used in some veterinary contexts. Using the wrong syringe type with the wrong calibration leads to a 2.5× dosing error.
How many doses are in a single vial?+
Doses per vial equals the total peptide mass in micrograms (vial mg × 1000) divided by your per-dose target in micrograms. A 5 mg vial dosed at 250 μg yields 20 doses.
Is bacteriostatic water the same as sterile water?+
No. Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits bacterial growth and allows a multi-dose vial to remain usable for up to 28 days refrigerated. Plain sterile water has no preservative and is intended for single use.
Is this calculator medical advice?+
No. This tool is for educational reference only. Always verify reconstitution and dosing instructions with your prescribing clinician or compounding pharmacist before injection.