What Is Bacteriostatic Water?
Bacteriostatic water is sterile water that contains 0.9% benzyl alcohol, a preservative that stops bacteria from multiplying. That preservative is what allows a reconstituted multi-dose vial to be drawn from repeatedly over time.
Why the benzyl alcohol matters
Plain sterile water has no preservative, so once a vial is opened it is intended for a single use. The 0.9% benzyl alcohol in bacteriostatic water is bacteriostatic — it holds bacterial growth in check — which is why it is the common choice for peptides that are dosed over several days or weeks.
Bacteriostatic water vs sterile water vs reconstitution solution
Sterile water: no preservative, single-use.
Bacteriostatic water: 0.9% benzyl alcohol, multi-use over time.
Reconstitution solution: a general term for whatever diluent a product specifies; it is often bacteriostatic water, but always check the label.
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Open the calculator →Frequently asked questions
Is reconstitution solution the same as bacteriostatic water?+
"Reconstitution solution" is a general term for the diluent used to mix a lyophilized peptide. It is frequently bacteriostatic water, but not always — some products specify sterile water or another diluent. Always follow the specific product label.
How much benzyl alcohol is in bacteriostatic water?+
Standard bacteriostatic water contains 0.9% benzyl alcohol by volume.