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.
Frequently asked questions
What is bacteriostatic water?
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol, a preservative that inhibits bacterial growth. This is what allows a vial to be accessed multiple times over several weeks.
What's the difference between bacteriostatic and sterile water?
Sterile water contains no preservative and is intended for single use. Bacteriostatic water contains benzyl alcohol, which inhibits bacterial growth and allows multi-dose use over roughly 28 days.
Can you use regular water for peptides?
No. Tap or distilled water is not sterile and is not appropriate for injection. Bacteriostatic water is the standard choice for peptide reconstitution.
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.