How to Reconstitute Peptides — Step by Step

What you need

• The peptide vial (a small glass vial with a rubber stopper and a puck of white powder)
• Bacteriostatic water (sterile water with 0.9% benzyl alcohol as a preservative)
• One larger syringe (3 mL) for transferring water, plus alcohol swabs
• Your insulin syringes (U-100, usually 0.5 mL or 1 mL) for dosing

Let the vial and water come to room temperature before you start; cold water dissolves powder more slowly.

Step by step

1. Wash your hands and wipe both rubber stoppers with an alcohol swab. Let them dry.
2. Draw the water. Pull the volume your pharmacy specified — commonly 1, 2, or 3 mL — into the transfer syringe.
3. Inject it slowly down the inside wall of the peptide vial. Aim the needle at the glass, not the powder. A direct stream can damage the peptide's structure.
4. Swirl, don't shake. Roll the vial gently between your fingers until the solution is clear. Shaking creates foam and can denature the peptide.
5. Label it with the date and the concentration (for example "5 mg / 2 mL = 2,500 mcg/mL").
6. Refrigerate at 2–8 °C, away from light, and note the beyond-use date from your pharmacy label.

Choosing how much water to add

Your pharmacy or provider will usually specify the volume, but it helps to understand why. The water volume does not change how much peptide you have — it changes how concentrated it is, and therefore how many syringe units each dose takes.

Take a 5 mg vial of BPC-157 and a prescribed dose of 250 mcg:

More water means a bigger, easier-to-read draw for small doses. Less water keeps large doses inside a single syringe: a 2.5 mg dose of TB-500 from a 10 mg vial is 25 units with 1 mL of water and 50 units with 2 mL. Pick the volume that puts your prescribed dose at a comfortable number of units — the reconstitution calculator does the arithmetic instantly for any vial.

The math, once

Three lines cover every case:

concentration (mcg/mL) = vial mg × 1,000 ÷ water mL
volume (mL)            = dose mcg ÷ concentration
units (U-100)          = volume mL × 100

For 5 mg in 2 mL and a 250 mcg dose: 2,500 mcg/mL → 0.1 mL → 10 units. Every compound calculator shows this working under "show the math."

Reading a U-100 insulin syringe

U-100 syringes are marked in units, where 100 units = 1 mL. A 1 mL syringe has 100 unit marks; a 0.5 mL syringe has 50, spaced further apart, which makes small doses easier to read accurately. Draw to the line, check for air bubbles (tap and push them out), and re-check the number before injecting.

Storage and handling

• Unopened vials: refrigerate; many peptides are stable for months when lyophilized and kept cold and dark.
• Reconstituted vials: refrigerate and use within the beyond-use date on your label, commonly 14–28 days.
• Travel: an insulated pouch with a cold pack is fine for a day; avoid freezing.
• Discard any vial that is cloudy, discoloured, or past its date, or whose stopper has been punctured many dozens of times.

Next: how to give a subcutaneous injection.

FREQUENTLY ASKED

SOURCES

1. USP General Chapter <797> Pharmaceutical Compounding — Sterile Preparations