What do you reconstitute peptides with?

Bacteriostatic water (sterile water with 0.9% benzyl alcohol) is the standard solvent because the preservative inhibits microbial growth and lets the reconstituted vial be stored for up to ~28 days under refrigeration.

How much bacteriostatic water do I add?

It depends on the desired concentration. A common ratio is 2 mL of BAC water per 5 mg vial, giving 2.5 mg/mL. Always calculate based on the planned experimental concentration.

How long do reconstituted peptides last?

Most reconstituted peptides remain stable for 14–28 days when stored at 2–8°C (refrigerated) and protected from light. Lyophilized (dry) peptides last 24+ months at -20°C.

How to reconstitute peptides: a step-by-step lab procedure

A clear step-by-step guide to reconstituting lyophilized research peptides with bacteriostatic water — including BAC water volume calculation, sterile technique, and storage.

For in-vitro laboratory research only. This is a procedural reference for handling lyophilized peptide vials in a research setting — not medical, dosing, or clinical guidance.

What you'll need

Lyophilized peptide vial (kept on ice if just removed from -20°C)
Bacteriostatic water (BAC water — sterile water + 0.9% benzyl alcohol)
Sterile insulin syringe (1 mL / 100 IU) or measured pipette
Alcohol prep pads
Lab notebook for the reconstitution log

Step 1 — Calculate your volume

Decide the target concentration first, then work out how much BAC water to add. Example: for a 5 mg vial at 2.5 mg/mL, add 2 mL of BAC water. For 5 mg/mL, add 1 mL. The peptide mass does not change — only the solvent volume.

Step 2 — Bring vials to room temperature

Let the lyophilized vial sit at room temperature for 5–10 minutes. Adding cold solvent to a frozen vial can cause condensation and degrade the powder.

Step 3 — Sterilize the stoppers

Wipe both vial stoppers (peptide and BAC water) with separate alcohol pads and let them air-dry for ~30 seconds.

Step 4 — Draw the BAC water

Pull air into the syringe equal to your target volume, inject it into the BAC water vial (this equalizes pressure), invert, and slowly draw out the calculated volume.

Step 5 — Add solvent down the side of the peptide vial

Insert the needle at an angle and let the BAC water trickle slowly down the inside wall of the peptide vial. Hitting the powder directly with a hard stream can shear and denature the peptide.

Step 6 — Dissolve gently

Do not shake. Swirl the vial gently between your fingers, or let it sit for 1–2 minutes. The powder should fully dissolve into a clear solution. Cloudy or particulate solutions indicate degradation — discard.

Step 7 — Label & store

Label the vial with the peptide name, concentration (mg/mL), date of reconstitution and your initials. Store at 2–8°C (refrigerated, protected from light). Use within ~28 days.

Storage cheat sheet

Lyophilized (dry): 24+ months at -20°C, sealed and dry
Reconstituted: 14–28 days at 2–8°C, protected from light
Never freeze/thaw a reconstituted vial repeatedly — aliquot if needed