Bacteriostatic vs. Sterile Water
Understanding the critical differences, shelf-life implications, and when to use which solvent.
The Critical Difference
Not all water is created equal when it comes to peptide research. Choosing the wrong solvent can lead to bacterial infections or rapid degradation of your compounds.
Sterile Water (SW)
What it is: Pure, distilled water that has been sterilized. It contains no additives.
Use case: Single-use injections only. Once a vial of sterile water is opened or punctured, it has no defense against bacteria. Any peptide reconstituted with plain Sterile Water should theoretically be used immediately.
Bacteriostatic Water (Bac Water)
What it is: Sterile water with 0.9% Benzyl Alcohol added.
The Magic of Benzyl Alcohol: This additive does two things:
- Antimicrobial: It prevents bacteria from reproducing inside the vial. This allows you to draw from the same vial multiple times (multi-dose) safely for up to 28 days.
- Preservative: It helps maintain the pH balance and stability of the solution.
Which Should You Use?
For almost all peptide protocols (Semaglutide, Tirzepatide, etc.), Bacteriostatic Water is the gold standard. Since these protocols involve weekly doses from the same vial over a month or more, you absolute need the antimicrobial protection.
Safety Warning
Never use tap water or bottled drinking water.
These contain minerals and bacteria that are harmless to drink but dangerous to inject. Always use pharmaceutical-grade solvents.
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