← All resources

How to Reconstitute Peptides: A Step-by-Step Guide

Published: 2026-08-29 · PeptApp

Peptides usually arrive as a freeze-dried (lyophilized) powder that must be dissolved before use. That step — reconstitution — is simple, but it sets the concentration your every dose depends on, so it pays to get the math and the technique right.

What you need

• The lyophilized peptide vial
• Bacteriostatic water (BAC water) — sterile water with 0.9% benzyl alcohol, which keeps a multi-dose vial usable
• A sterile syringe for transferring the water
• Alcohol swabs for both vial tops

Plain sterile water works for a single immediate use, but a vial you will draw from for weeks needs bacteriostatic water.

The math: concentration decides everything

The only formula that matters: concentration = peptide mass ÷ water volume. Add 2 ml of water to a 5 mg vial and you have 2.5 mg/ml. Add 4 ml instead and you have 1.25 mg/ml — same peptide, half the concentration, doubled injection volumes.

More water means larger, easier-to-measure volumes per dose — helpful when doses are tiny. Less water means smaller injections. A peptide reconstitution calculator does this in both directions; PeptApp’s calculator also converts the result straight into syringe units.

Step by step

1. Wash your hands; swab the tops of both vials with alcohol and let them dry.
2. Draw the chosen volume of bacteriostatic water into the syringe.
3. Insert the needle through the peptide vial’s stopper and aim the stream at the glass wall, not the powder — let the water run down gently.
4. Swirl softly until fully dissolved. Never shake: mechanical stress can damage peptide chains.
5. Label the vial with the date and the concentration.
6. Refrigerate. The expiry clock starts now.

Mistakes that ruin vials

• Shaking instead of swirling.
• Blasting the powder with a direct stream of water.
• Too little water, leaving doses too small to measure accurately on a syringe.
• No label — two weeks later, nobody remembers the date or the concentration.

After reconstitution

A reconstituted vial is on a clock: keep it refrigerated, inspect it for clarity before each draw, and track when it should be discarded. PeptApp stamps the reconstitution date automatically, watches the expiry for you, and keeps a per-vial inspection log.