Reconstitution Guide

Why Peptides Come as a Powder

Peptides are fragile in solution. Freeze-drying removes water and leaves a stable powder that survives shipping and long storage. Adding liquid back—reconstitution—reactivates the peptide for use and starts a shelf-life clock, because once dissolved the peptide slowly degrades even under refrigeration.

The liquid of choice is bacteriostatic water: sterile water containing 0.9% benzyl alcohol, which suppresses bacterial growth and allows a multi-dose vial to be used over several weeks. Plain sterile water or saline lacks the preservative and is only appropriate for single use.

What You Need

• The lyophilized peptide vial
• Bacteriostatic water (for multi-use vials)
• Insulin syringes, U-100, typically 29–31 gauge
• Alcohol swabs
• A clean, flat work surface

Step by Step

1. Swab both vials. Wipe the rubber stopper of the peptide vial and the bacteriostatic water vial with alcohol and let them dry. 2. Draw your water. Pull the chosen volume of bacteriostatic water into the syringe. 3. Add it slowly. Insert the needle at an angle and let the water run down the inside wall of the vial—never spray it directly onto the powder, which can damage the peptide and cause foaming. 4. Do not shake. Gently swirl or let the vial sit until the powder fully dissolves into a clear solution. Shaking shears the peptide and creates froth. 5. Refrigerate. Store the reconstituted vial at 2–8 °C (standard fridge) away from light.

The Concentration Math

This is the part people overthink. Concentration is just total peptide divided by total water:

Concentration (mg/mL) = peptide amount (mg) ÷ bacteriostatic water added (mL)

Example: a 5 mg peptide vial reconstituted with 2 mL of water gives 2.5 mg/mL, or 2500 mcg/mL.

To find your draw volume for a target dose:

Draw (mL) = desired dose (mg) ÷ concentration (mg/mL)

Continuing the example, for a 250 mcg (0.25 mg) dose: 0.25 ÷ 2.5 = 0.1 mL.

Reading an Insulin Syringe

U-100 insulin syringes are marked in units, where 100 units = 1 mL. So 0.1 mL = 10 units. In the example above, a 250 mcg dose is drawn to the 10-unit mark. This is the single most useful conversion to memorize:

• 1.0 mL = 100 units
• 0.5 mL = 50 units
• 0.1 mL = 10 units
• 0.01 mL = 1 unit

A practical tip: choosing your water volume to make the math clean is worth it. Reconstituting a 5 mg vial with exactly 2 mL means every 10 units equals 250 mcg—easy to titrate without a calculator.

Storage and Shelf Life

• Lyophilized (unopened) powder: stable for months to years in a freezer; check the certificate of analysis for the specific compound.
• Reconstituted solution: generally used within 3–4 weeks when refrigerated, though this varies by peptide. Fragile peptides degrade faster.
• Protect from light and heat. Keep vials in their box in the back of the fridge, not the door.
• Never freeze a reconstituted vial unless the specific peptide is known to tolerate it—ice crystals can denature the molecule.

Discard any vial that becomes cloudy, develops particulates, or changes color, and always note the reconstitution date on the vial.

A Note on Safety and Scope

Reconstitution technique is presented here for education. The peptides discussed on Learn Peptide are research compounds, most of which are not approved for human use. Sterile technique, appropriate materials, and qualified oversight matter for any real-world handling. This guide explains the chemistry and math—it is not a substitute for medical or laboratory supervision.