Reconstitution is dissolving a lyophilized peptide powder in a sterile diluent (typically bacteriostatic water) to produce a measurable solution. The dose math: mg of peptide divided by mL of bacteriostatic water gives the mg/mL concentration. On a standard U-100 insulin syringe, 1 IU = 0.01 mL. Refrigerate the reconstituted vial at 2–8°C, protect from light, and use within 14–30 days for most peptides.
What reconstitution is — and why peptides ship as dry powder
Lyophilized peptides ship as dry powder in vials. Reconstitution is the process of dissolving the powder in a sterile diluent — typically bacteriostatic water — to produce a solution that can be measured and dosed.
This guide covers the mechanics from a research-protocol perspective. None of it is human-use guidance.
The dose math: mg ÷ mL = concentration
The relationship between mg of peptide, mL of bacteriostatic water, and dose-volume in IU on an insulin syringe is straightforward but easy to get wrong. The shortcut: (mg of peptide ÷ mL of bacteriostatic water) gives mg/mL concentration. From there, multiply by the dose volume in mL to get the dose in mg.
Most research uses 1 IU = 0.01 mL on a standard insulin syringe.
Storage: refrigerated, light-protected, 14–30 days
After reconstitution, peptides should be refrigerated (2–8°C) and protected from light. Most peptides are stable for 14–30 days at refrigerator temperature; longer storage requires freezing in single-dose aliquots to avoid freeze-thaw cycles.
Related reading
- BPC-157 vendor leaderboard — for those reconstituting the most common research peptide.
- Retatrutide dosing protocols — the dose-volume math worked through for the GLP-1 class specifically.
- How to verify a Janoshik COA — before you bother reconstituting, confirm the vial's identity.
- Use our peptide dose calculator if you want the mg-mL-IU math computed automatically.
Frequently asked
What is bacteriostatic water and why is it used for peptide reconstitution?
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a preservative. The benzyl alcohol inhibits microbial growth, which lets a multi-dose vial be used over multiple days without contamination. Plain sterile water is also usable but only for single-day reconstitution (no preservative), and most research protocols default to bacteriostatic water for that reason.
How do I calculate the dose for a reconstituted peptide vial?
Two steps. First, divide the vial's labeled mg of peptide by the mL of bacteriostatic water you added — that gives the concentration in mg/mL. Second, multiply the concentration by your target dose in mL. On a U-100 insulin syringe, each 1-unit mark equals 0.01 mL. Example: a 5 mg vial reconstituted with 2 mL of bacteriostatic water yields 2.5 mg/mL. A 250 mcg dose is 0.1 mL, which is 10 units on the U-100 syringe.
How long does a reconstituted peptide last in the refrigerator?
Most peptides reconstituted with bacteriostatic water are stable for 14–30 days at refrigerator temperature (2–8°C), protected from light. The exact stability window varies by peptide — BPC-157 and TB-500 are at the longer end, while glucagon-class compounds and unstable analogs are at the shorter end. Longer-term storage requires freezing single-dose aliquots to avoid freeze-thaw cycles, which degrade most peptides.
What syringe should I use for research peptide reconstitution?
Standard U-100 insulin syringes with a 27-31 gauge, 0.5-inch needle are the typical research-protocol choice. They're calibrated in units where 1 unit = 0.01 mL, which simplifies the dose math. For larger volumes (more than 1 mL), a 1 mL or 3 mL tuberculin syringe with mL graduations is more readable than counting 100 insulin units.