Guide

How to Reconstitute Peptides: Step-by-Step

ReconstitutionReconstitutionThe process of mixing a freeze-dried (lyophilized) peptide powder with bacteriostatic water to create a solution of known concentration.See glossary → is the process of mixing a freeze-dried peptide powder with bacteriostatic waterBAC water (bacteriostatic water)Sterile water containing 0.9% benzyl alcohol, which suppresses bacterial growth. It is the standard diluent used to reconstitute lyophilized peptides for multi-dose research vials.See glossary → to create a solution of known concentration. Every injectable peptide arrives lyophilizedLyophilizedFreeze-dried. Peptides are shipped as a lyophilized powder ('puck') because the dry form is far more stable than a solution. It must be reconstituted before use in research.See glossary → — as a small white puck or powder in a sealed vialVialThe small sealed glass container peptides are supplied in, topped with a rubber septum that a syringe needle can pass through.See glossary → — because the dry form survives shipping and storage far better than a liquid. Before any research use, that powder has to become a measurable solution. This guide walks through the process step by step, with the math.

What you need

Missing something? See the Canadian supplies guide for where to source each item.

Step 1 — Decide how much water to add

This is the step that sets your concentration, and it is where most mistakes happen. The formula:

Concentration = vial contents (mg) ÷ water added (mL)

Add 2 mL to a 5 mg vial and you get 2.5 mg/mL (2,500 mcg/mL). Add 1 mL to the same vial and you get 5 mg/mL. Neither is more "correct" — but more water produces larger injection volumes that are easier to measure accurately on a U-100 syringeU-100 syringeAn insulin syringe calibrated so that 100 units equal 1 mL. The standard syringe referenced in peptide research; each unit equals 0.01 mL.See glossary →. For small doses (under 500 mcg), 2–3 mL per vial keeps the syringe math comfortable.

Step 2 — Prepare both vials

1. Let the peptide vial come toward room temperature for a few minutes (cold glass plus warm water invites condensation).
2. Flip off the plastic caps on both the peptide vial and the BAC water vial.
3. Swab both rubber stoppers with an alcohol swab and let them air-dry.

Step 3 — Draw the bacteriostatic water

Draw your chosen volume of BAC water into the mixing syringe. If your syringe is smaller than the total volume, repeat the fill — the math still works, just track the total.

Step 4 — Add the water slowly

Insert the needle through the peptide vial's stopper at an angle, aiming the stream at the glass wall, not the powder. Depress the plunger slowly. Peptides are fragile chains of amino acidsAmino acidThe chemical building block of peptides and proteins. Peptides are short chains of amino acids linked together by peptide bonds.See glossary →; a direct jet onto the powder can damage them.

Step 5 — Swirl, never shake

Gently swirl or roll the vial until the solution is clear. Most peptides dissolve within a minute or two; some take longer. Never shake the vial — mechanical shear can denature the peptide. A cloudy solution after full dissolution, or visible particles that won't dissolve, are red flags worth documenting and raising with the vendor.

Step 6 — Label and refrigerate

Write the date and the concentration on the vial. Reconstituted peptides live in the fridge at 2–8°C — see the storage guide for compound-specific stability windows.

The dose math, worked

Say you reconstituted a 5 mg BPC-157 vial with 2 mL of BAC water, and the research literature references a 250 mcg dose:

1. Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL = 2,500 mcg/mL
2. Volume needed: 250 mcg ÷ 2,500 mcg/mL = 0.1 mL
3. On a U-100 syringe: 0.1 mL × 100 units/mL = 10 units

Same math, every peptide: dose ÷ concentration = volume, then volume × 100 = units. If reading syringe markings is new territory, the syringe guide covers U-100 markings, dead space, and the classic errors.