How to Reconstitute Peptides
Reconstitution is the process of turning a freeze-dried (lyophilized) peptide powder into an injectable solution by adding a sterile liquid — usually bacteriostatic water. This guide walks through the process and the arithmetic behind an accurate dose.
What you need
A vial of lyophilized peptide, bacteriostatic water (or the diluent specified on the label), an appropriately sized syringe for adding water, and U-100 insulin syringes for dosing.
Alcohol swabs and a clean, flat surface. Work slowly and let the vial reach room temperature first.
Step 1 — Decide how much water to add
The amount of bacteriostatic water you add sets the concentration. More water = more dilute = larger, easier-to-read draws on the syringe. Less water = more concentrated = smaller draws.
The volume of water does not change the total amount of peptide — only how it is spread out. Use the calculator on this site to pick a water amount that lands your dose on a round number of units.
Step 2 — Add the water gently
Draw the chosen volume of bacteriostatic water into a syringe. Insert the needle into the vial and let the water run slowly down the inside wall of the glass — do not spray it directly onto the powder.
Never shake the vial. Swirl it gently and let it sit; the powder will dissolve on its own within a minute or two.
Step 3 — Calculate and draw your dose
Once mixed, the concentration is fixed. To find how many insulin-syringe units equal your target dose, use the identity: units = dose (mcg) × water (mL) ÷ (10 × vial (mg)).
The peptide calculator does this for you and shows the exact units to draw. Store the reconstituted vial in the refrigerator.
Ready to calculate your dose?
Use the free peptide reconstitution calculator to convert any dose into insulin-syringe units.
Open the calculator →Frequently asked questions
How much bacteriostatic water should I add to a peptide vial?+
There is no single correct amount — it only changes the concentration. A common approach is to add enough water so your intended dose lands on a round, easy-to-read number of units (often 1–3 mL for a 5–10 mg vial). Use the calculator to find the ideal amount.
Can I use regular water or sterile water instead of bacteriostatic water?+
Bacteriostatic water contains 0.9% benzyl alcohol, which limits bacterial growth and lets a multi-dose vial be used over time. Sterile water has no preservative and is generally used for single-dose situations. Follow the diluent specified on your product label.
How long does a reconstituted peptide last?+
Once mixed, most peptides are kept refrigerated and used within a few weeks. Always follow the storage guidance on your specific product; degradation timelines vary by peptide.