Bacteriostatic Water (BAC Water)
Sterile water with a preservative, commonly used to reconstitute peptides.
Bacteriostatic water is sterile water containing a small amount of preservative (typically benzyl alcohol) that inhibits bacterial growth, which is why it’s often chosen for reconstituting multi-use vials.
In PeptideWiz, the volume of liquid you add during reconstitution is one of the inputs the calculator uses to determine concentration and syringe units.
Not medical advice. PeptideWiz is a tracking and organization tool. These definitions are general education only — not medical advice, a recommendation, or instructions for use. Always work with a licensed medical provider.
Frequently asked questions
What is bacteriostatic water made of?
Bacteriostatic water is sterile water for injection that contains a small amount of a preservative, most commonly 0.9% benzyl alcohol, which slows the growth of bacteria. This preservative is what allows a vial to be entered more than once over a limited period, unlike single-use sterile water. For the full product details, see the DailyMed label.
How is bacteriostatic water different from sterile water?
The main difference is the preservative: bacteriostatic water contains benzyl alcohol that inhibits bacterial growth, while sterile water for injection contains no preservative and is intended for single use. Because of the preservative, a bacteriostatic vial can typically be accessed multiple times within a manufacturer-stated window. Which diluent is appropriate for a given product is a decision for a licensed healthcare provider, not something PeptideWiz determines for you.
Why is bacteriostatic water used to reconstitute peptides?
Many peptides are supplied as a freeze-dried (lyophilized) powder that must be mixed with a liquid before use, a step called reconstitution. Bacteriostatic water is commonly chosen because its preservative helps limit microbial growth across the multiple withdrawals a vial may see. PeptideWiz provides general education and record-keeping only; the choice of diluent should follow the guidance of your provider and the product's labeling.
How long is bacteriostatic water good for after opening?
Manufacturer labeling for bacteriostatic water for injection commonly references a limited in-use period, often up to 28 days, after the vial is first entered. Storage conditions and the specific product both affect this, so always follow the instructions on the label and any direction from your provider. You can log opened-vial dates in PeptideWiz to help keep track, but the app does not set or verify expiration for you.
Is bacteriostatic water safe for everyone?
Bacteriostatic water contains benzyl alcohol, a preservative that is generally not recommended for certain populations such as newborns, and some people may have sensitivities. Whether it is appropriate for you is a medical question that belongs to a licensed healthcare provider who knows your history. PeptideWiz offers general education only and does not diagnose, treat, or make product-safety determinations.