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

If you've ever stared at a vial of lyophilized peptide wondering how much bacteriostatic water to add — and then how many units to draw for your dose — you're not alone. Reconstitution is the step that trips up almost everyone starting out. This guide walks through it clearly.

What "reconstitution" actually means

Peptides ship as a lyophilized (freeze-dried) powder because they're unstable in liquid for long periods. Reconstitution means adding a sterile liquid — almost always bacteriostatic water (water with 0.9% benzyl alcohol, which prevents bacterial growth) — to dissolve the powder into an injectable solution.

Step by step

1. Let both vials reach room temperature. Cold vials can cause the powder to dissolve unevenly.
2. Wipe both stoppers with an alcohol swab.
3. Draw your bacteriostatic water into a syringe — the amount you choose determines your concentration (more on that below).
4. Add the water slowly, aiming the stream down the inside wall of the vial rather than blasting directly onto the powder. Peptides are delicate.
5. Swirl gently — never shake. Shaking can damage the peptide. Let it dissolve; it usually clears within a minute or two.
6. Store it refrigerated (2–8°C) once reconstituted.

The part everyone gets wrong: the math

Here's the key insight — the same vial can be diluted many different ways. How much water you add sets your concentration, and that changes how many units you draw for the same dose.

The formula:

• Concentration = total peptide (mcg) ÷ water added (mL)
• Units to draw = your dose (mcg) ÷ concentration × 100  (on a U-100 insulin syringe)

Example: a 5 mg vial (5,000 mcg) reconstituted with 2 mL of water gives a concentration of 2,500 mcg/mL. For a 250 mcg dose, that's 250 ÷ 2,500 × 100 = 10 units.

Common mistakes to avoid

• Shaking the vial — always swirl.
• Using the wrong water — sterile water has no preservative and is only good for single use; bacteriostatic water lasts weeks refrigerated.
• Forgetting your concentration — if you redo a vial with a different water amount, your units change. Track it.

Frequently asked questions

How do you reconstitute a peptide?

Let the vial reach room temperature, swab both stoppers with alcohol, draw your bacteriostatic water, and inject it slowly against the glass wall of the vial so it runs down onto the powder. Swirl gently — never shake.

Why can't you shake a peptide vial?

Peptides are fragile protein chains. Shaking creates shear force and foaming that can damage them. Gentle swirling or letting it dissolve on its own is the standard approach.

What water do you use to reconstitute peptides?

Bacteriostatic water is standard because it contains a preservative (benzyl alcohol) that allows the vial to be used over multiple weeks. Sterile water has no preservative and gives a much shorter window.

For educational and research purposes only. Not medical advice. Consult a physician before starting any peptide protocol. BioHack is a tracking tool and does not sell peptides.