What Is Bacteriostatic Water?
If you're reconstituting peptides, one term comes up constantly: bacteriostatic water. Here's what it is, why it matters, and how it differs from other options.
What is bacteriostatic water?
Bacteriostatic water is sterile water that contains 0.9% benzyl alcohol as a preservative. The benzyl alcohol prevents bacterial growth, which is what makes it "bacteriostatic" — it lets you use the same vial multiple times over several weeks without it becoming contaminated.
Bacteriostatic vs. sterile water
- Sterile water has no preservative. It's intended for single use — once you puncture the vial, it should be used and discarded.
- Bacteriostatic water has the preservative, so a reconstituted peptide stays usable for the multiple weeks it takes to work through a vial.
For most peptide reconstitution, bacteriostatic water is the standard choice precisely because peptides are dosed over time.
How much do you add?
There's no single "right" amount — how much you add sets your concentration, which determines how many units you draw per dose. More water = more dilute = more units per dose (easier to measure small doses). Less water = more concentrated = fewer units.
BioHack's reconstitution calculator shows exactly how your water amount changes the units to draw.
Storage
Keep bacteriostatic water at room temperature before use. Once you've reconstituted a peptide with it, store the solution refrigerated (2–8°C) and protect it from light.
BioHack turns everything above into a tool — a reconstitution calculator, dose advisor, cycle planner, and 45-peptide library, all in one app.
Open BioHack →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.