How to Reconstitute Peptides

Most research peptides ship as a freeze-dried powder. You add bacteriostatic water before you can draw a dose. That process is called reconstitution.

What you need

• The sealed peptide vial
• Bacteriostatic water (BAC water), usually 1 to 3 mL per vial depending on the protocol
• A drawing syringe with a longer needle (often 21G or 23G)
• An insulin syringe (U-100) for dosing
• Alcohol prep pads
• A clean, flat surface

The procedure

1. Wash your hands. Wipe both rubber stoppers (peptide vial and BAC water vial) with a fresh alcohol pad.
2. Draw your chosen volume of BAC water into the drawing syringe.
3. Insert the needle into the peptide vial at an angle so the water runs down the inside wall instead of splashing onto the powder.
4. Let the powder dissolve on its own. If it's slow, swirl the vial gently. Don't shake it.
5. The vial is now reconstituted. Store it in the refrigerator between 2 and 8 °C.

The amount of water you add determines your concentration, which determines how many units you draw on the insulin syringe. Match the protocol's recommended water volume, or run the new number through the reconstitution calculator.

Common mistakes

• Wrong water volume. Adding 3 mL when the protocol expects 2 mL throws off every future dose by 33%.
• Spraying water onto the powder. Some peptides are sensitive to mechanical stress. Run the water down the wall.
• Shaking the vial. Same reason. Gentle swirl only.
• Skipping the alcohol wipe. Contamination risk is small but real, especially with multi-use vials.
• Reusing needles. They go dull fast and increase tissue damage on injection.

After reconstitution

A reconstituted vial is good for 28 days in most cases, since bacteriostatic water contains 0.9% benzyl alcohol that suppresses bacterial growth. Track the date on the vial. Throw it out at 28 days even if there's product left.

For how to read the syringe markings once your dose is calculated, see Understanding Syringe Units.

FAQ

What does it mean to reconstitute a peptide?
Most research peptides ship as a freeze-dried powder. Reconstitution is the process of adding bacteriostatic water to that powder so the peptide is dissolved and you can draw a dose.

What water do you use to reconstitute peptides?
Bacteriostatic water, usually 1 to 3 mL per vial depending on the protocol. It contains 0.9% benzyl alcohol, which suppresses bacterial growth and lets a multi-use vial stay usable for several weeks.

Should you shake the vial to dissolve the powder?
No. Insert the needle at an angle so the water runs down the inside wall instead of splashing onto the powder, then let it dissolve on its own. If it is slow, swirl the vial gently. Some peptides are sensitive to mechanical stress, so a hard shake can damage them.

Why does the amount of water matter?
The volume of water you add sets the concentration, which determines how many units you draw on the insulin syringe. Adding 3 mL when the protocol expects 2 mL throws off every future dose by 33%. Match the protocol's recommended water volume, or run the new number through the reconstitution calculator.

How long does a reconstituted vial last?
With bacteriostatic water, a reconstituted vial is commonly usable for up to 28 days, because its 0.9% benzyl alcohol suppresses bacterial growth. That 28-day figure is a sterility limit for a multi-use vial, not a universal stability guarantee — some peptides degrade faster, so follow peptide-specific guidance where it exists. Track the date on the vial and discard at 28 days even if there is product left.

How should you store a reconstituted vial?
Most reconstituted peptides keep best refrigerated between 2 and 8 °C, protected from light. A few are handled differently — held at room temperature for a shorter window — so check the guidance for your specific peptide (for example, tesamorelin is typically kept at room temperature and used within about 7 days).