Peptide Reconstitution Calculator
Last updated July 2, 2026 · Medically reviewed by David Chen, MD, PhD
Peptides arrive as freeze-dried powder and must be reconstituted with bacteriostatic water into a clear liquid of known concentration before any dose can be measured accurately. The calculator below works out how much water to add and what each dose draws up on the syringe.
Reconstitution calculator
An insulin syringe is marked in “units” instead of mL: on the standard U-100 scale, 100 units equal 1 mL, so each unit is 0.01 mL. This calculator turns a vial of peptide plus a measured volume of bacteriostatic water into a working concentration, then converts a target dose into the matching draw on your syringe.
How to reconstitute a peptide
Let the peptide vial and bacteriostatic water sit out for 15–20 minutes first — cold vials cause condensation and incomplete dissolving. Draw the calculated volume of water and add it slowly down the inside wall of the vial, aiming the stream at the glass rather than directly onto the powder. Let it dissolve on its own; swirl gently if needed, but never shake. The video below walks through the full process.
Bacteriostatic water — not sterile or distilled water — is what keeps a multi-dose vial safe to draw from over time; the benzyl alcohol in it inhibits bacterial growth. Read more in bacteriostatic water explained. Once your peptide is reconstituted, head to the dosing calculator to plan the escalation schedule.
Frequently asked questions
- How much bacteriostatic water should I add?
- There is no single right amount — it sets the concentration. Adding more water makes the solution more dilute (more units per dose); adding less makes it more concentrated. Enter the vial size and your target dose in the calculator and it returns the volume to add and what each dose measures on the syringe.
- What does the dose measure on an insulin syringe?
- Insulin syringes are marked in units, where 100 units equals 1 mL. The calculator converts your milligram dose into units at the concentration you choose, so you can draw it accurately.
- How should reconstituted peptide be stored?
- Store reconstituted peptide at 2–8°C (refrigerated) and unopened lyophilized vials at −20°C or colder, away from light. Label each vial with the compound, concentration, and reconstitution date.
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