Peptide Reconstitution Calculator
Figure out exactly how much to draw on your syringe. Enter your vial, water, and dose below.
Amount of peptide in the vial (check the label)
Enter your values
Fill in the fields to see exactly how much to draw on your syringe.
How to reconstitute a peptide
- Clean the vial tops — Wipe the rubber stopper of both the peptide vial and the bacteriostatic water vial with an alcohol swab. Let dry.
- Draw the water — Using a fresh syringe, draw the amount of bacteriostatic water you entered above from the BAC water vial.
- Add water to the peptide — Insert the needle into the peptide vial and slowly push the water down the inside wall of the vial. Don't spray it directly onto the powder.
- Swirl gently — Roll the vial between your palms or gently swirl until the powder is fully dissolved. Never shake — shaking can damage the peptide.
Frequently asked questions
What is bacteriostatic water?
Bacteriostatic water (BAC water) is sterile water with 0.9% benzyl alcohol added as a preservative. It's used to reconstitute peptides because the preservative prevents bacterial growth, allowing the solution to be used over multiple doses. Never use regular water — always use bacteriostatic water or the diluent specified by the manufacturer.
How much bacteriostatic water should I use?
The most common amount is 1–2 mL per vial. Using less water gives a more concentrated solution (fewer units per dose), while more water makes it easier to measure small doses accurately. There's no single right answer — use this calculator to see how your water volume affects the number of units per dose.
What syringe size should I use?
Insulin syringes come in 0.3 mL (30 units), 0.5 mL (50 units), and 1 mL (100 units). Smaller syringes are more precise for small doses. If your calculated dose is under 15 units, a 0.3 mL syringe gives you the best accuracy. For most peptide doses, a 0.5 mL or 1 mL syringe works well.
How long does reconstituted peptide last?
Most reconstituted peptides last 3–4 weeks when stored in the refrigerator (2–8°C / 36–46°F). Never freeze reconstituted peptides, and avoid leaving them at room temperature. Some peptides like semaglutide and tirzepatide may last longer — check the specific peptide's storage guidelines.
What if I add too much water?
Adding too much water doesn't damage the peptide — it just makes the solution less concentrated, so you'll need to draw more per dose. Use this calculator to recalculate your dose with the actual water amount you added. The total peptide in the vial stays the same regardless of water volume.
This calculator is for informational and research purposes only. Not medical advice — consult a healthcare provider before using any peptide. Always verify your calculations before injecting anything.