How to Reconstitute a Peptide Vial — A Practical Guide

What "reconstitution" means

Most research peptides ship as a freeze-dried (lyophilized) powder in a glass vial. To inject them you mix the powder with bacteriostatic water — sterile water containing 0.9% benzyl alcohol as a preservative — to create a solution. The amount of water you add determines the concentration, which in turn determines how many "units" on a syringe equal your target dose.

The math, in one paragraph

Concentration (mg/mL) = vial mg ÷ bacteriostatic water mL.

So 5 mg of peptide reconstituted with 2 mL of BAC water = 2.5 mg/mL. A 250 mcg dose = 0.25 mg ÷ 2.5 mg/mL = 0.1 mL. On a U-100 insulin syringe (1 mL = 100 units), that's 10 units.

You can do all of this in our free reconstitution calculator, which also has a reverse mode: enter the units you want each dose to land on and it tells you exactly how much BAC water to add. That's the more common real-world question.

What you need

The peptide vial (lyophilized powder)
Bacteriostatic water (multi-dose vial, 0.9% benzyl alcohol)
Insulin syringes — U-100 is the most common; U-50 if you want finer precision on tiny volumes
Alcohol prep pads
Sharps container
Refrigerator for storage of the reconstituted vial

The procedure

Wash hands. Don't skip this.
Bring vials to room temperature for 10–15 minutes if they were refrigerated. Cold vials can crack when injected with water.
Wipe both vial stoppers with an alcohol pad.
Draw your BAC water into the syringe — slowly. Pull the plunger to the exact mL mark you calculated.
Inject the BAC water into the peptide vial, aiming for the side wall, not the powder directly. This minimizes foaming.
Roll the vial gently between your palms to dissolve. Do not shake. Shaking can denature peptides; rolling does not.
Wait 60 seconds for the powder to fully dissolve. The solution should be clear. If you see particulates, do not use it.
Refrigerate at 2–8°C. Most reconstituted peptides are stable for ~28 days at fridge temperature. Some are shorter; check your COA.

Common mistakes

Shaking the vial. Roll, don't shake.
Using regular saline or distilled water. Use bacteriostatic water specifically — the benzyl alcohol prevents bacterial growth across multiple draws.
Forgetting your concentration. Label the vial with the date you reconstituted, the BAC water mL added, and the resulting concentration.
Not zeroing the syringe. A small air bubble at the tip changes the effective dose.
Using the wrong syringe units. A U-40 syringe at 10 units is not the same volume as a U-100 syringe at 10 units. Match the syringe to the math.

Storing the powder vial

Lyophilized peptides are stable for years at –20°C. At room temperature they degrade much faster — weeks for short peptides, months for stable ones. If you're not reconstituting today, freeze the vial.

Storing the reconstituted vial

After reconstitution: refrigerate, never freeze. Freezing damages peptide structure and creates particulates. Most vendors cite a 28-day fridge window; our vial life calculator tells you whether your protocol will finish the vial before the BAC water expires.

Disclaimer

This is an educational reference. Peptide use outside an FDA-approved indication should only happen under licensed-physician oversight.