Bacteriostatic water is sterile water mixed with 0.9% benzyl alcohol. The alcohol prevents bacterial growth, which is why the same vial can be used across multiple doses over several weeks. Regular sterile water for injection does not contain the preservative. It's single-use only. For any peptide you plan to draw from more than once, BAC water is the right choice.
Guide
What is BAC Water?
Compiled and maintained by the BACwater.ai editorial team and checked against the sources cited on this page. This is general research information, not a medical review. Last updated July 2026.
References
Primary sources for the facts on this page. We cite regulatory and peer-reviewed authorities rather than secondary blogs.
- Bacteriostatic Water for Injection, USP - prescribing information · U.S. FDA labeling via DailyMed (NIH / NLM)Defines bacteriostatic water as sterile water with 0.9% benzyl alcohol added as a bacteriostatic preservative, supplied in a multiple-dose container for diluting or dissolving drugs; contraindicated in neonates.
- Benzyl alcohol (Compound CID 244) · NIH PubChem, National Library of MedicineChemical identity, properties, and safety data for benzyl alcohol, the bacteriostatic preservative in BAC water.
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- ComparisonBAC Water vs Sterile Water
Bac water contains a benzyl alcohol preservative for multi-dose use. Sterile water has none and is single-use. Use bac water for peptide reconstitution.
- ComparisonBAC Water vs Saline
Saline is 0.9% sodium chloride with no preservative. Bac water adds benzyl alcohol for multi-dose use. Bac water is the standard choice for reconstitution.
- ComparisonBAC Water vs Sodium Chloride
0.9% sodium chloride is saline: salt water with no preservative. Bac water is preserved sterile water. Use bac water for multi-dose peptide reconstitution.
- ComparisonBAC Water vs Distilled Water
Distilled, deionized, and tap water are not sterile and not for injection. Only use bacteriostatic or sterile water to reconstitute peptides.