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How to reconstitute a peptide vial, step by step

Mixing a freeze-dried peptide with bacteriostatic water: what you need, the steps, how to work out the ml per dose and how long the vial keeps.

Most injectable peptides are sold as a freeze-dried powder. Before use, the powder has to be dissolved in bacteriostatic water: this is called reconstitution. The amount of water never changes the dose. It only changes how many ml each dose takes in the syringe.

What you need

• The peptide vial.
• Bacteriostatic water: sterile water with 0.9% benzyl alcohol, which stops bacteria from growing so the vial can be used for weeks.
• 1 ml insulin syringes with a fine needle.
• Alcohol swabs and a sharps container for used needles.

Step by step

1. Wash your hands. Clean the rubber tops of the peptide vial and the water vial with an alcohol swab and let them dry.
2. With a sterile syringe, draw the amount of bacteriostatic water you planned, for example 2 ml.
3. Insert the needle into the peptide vial and let the water run slowly down the inside wall. Do not squirt it straight onto the powder.
4. Swirl gently, or let the vial sit, until the powder has dissolved completely. Never shake it: shaking can damage the peptide.
5. Write the date and the concentration on the vial and put it in the fridge.

How many ml is one dose?

Two simple steps. First the concentration: the amount in the vial divided by the ml of water. Then the volume: the dose divided by the concentration.

Example with BPC-157: a 5 mg vial mixed with 2 ml of water holds 2.5 mg per ml. A dose of 500 mcg (0.5 mg) is 0.5 ÷ 2.5 = 0.20 ml. With only 1 ml of water, the same dose would be 0.10 ml: the same amount of peptide, in a smaller volume that is harder to measure well.

uPrime rounds every volume to steps of 0.05 ml, which you can read on a 1 ml syringe. The calculator does all of this for you, for any vial size and amount of water.

How much water should you add?

Choose an amount that puts each dose between about 0.05 ml and 1 ml. Below 0.05 ml the volume is too small to measure accurately; above 1 ml it no longer fits in one syringe. More water makes small doses easier to measure, and the vial still holds the same number of doses.

After mixing

• Keep the vial in the fridge at 2–8 °C, away from light.
• Most mixed peptides keep for about 4 weeks. Each compound page in uPrime shows how long its vial keeps.
• Never freeze a mixed vial. Throw it away if it turns cloudy, changes color or shows particles.
• Use a new sterile needle every time you draw from the vial.

Educational reference only. It is not medical advice and does not recommend any compound or dose. Talk to a doctor before using any of these compounds.

Last reviewed: 2026-10-26

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