Quick comparison
| Property | Bacteriostatic water | Sterile water | Distilled water |
|---|---|---|---|
| Preservative | 0.9% benzyl alcohol | None | None |
| Sterile? | Yes | Yes | Not guaranteed |
| Repeated entry? | Yes (multi-dose) | No (single-use) | No |
| Typical in-use window once opened | ~28 days | Discard after one use | N/A |
| Made for laboratory reconstitution? | Yes | Yes (single draw) | No |
Bacteriostatic water
Bacteriostatic water is sterile water with 0.9% benzyl alcohol added. The preservative inhibits bacterial growth, so a sealed multi-dose vial can be entered with a sterile needle multiple times without losing sterility. This is the format laboratories reach for when a diluent vial is drawn down over several sessions rather than all at once. Full explainer here.
Sterile water
Sterile water for injection is purified and sterilized but contains no preservative. It is sterile in the sealed container and remains so only until the first needle entry. Because nothing suppresses microbial growth afterward, it is labelled single-dose and discarded after one use. It is a fine diluent for a one-shot preparation, but it is the wrong tool when you need to re-enter the same vial.
Distilled water
Distilled water has simply been purified by boiling and condensing it back to liquid, which removes minerals and many contaminants. It is not necessarily sterile, and it is not injection-grade. Distilled water is appropriate for general laboratory tasks like rinsing glassware or preparing buffers from scratch — not as a sterile reconstitution diluent. Do not substitute it where a sterile, preserved diluent is required.
Which should you use?
For repeated-entry laboratory reconstitution, bacteriostatic water is the format designed for the job — the preservative is what makes a multi-dose vial possible. Sterile water works only when you will use the entire diluent in a single draw. Distilled water is not a substitute for either in sterile work.
Our 10 mL multi-dose bacteriostatic water is sterile-filtered, made with 0.9% benzyl alcohol, and documented to the lot. See the product.
Frequently asked questions
Can I use sterile water instead of bacteriostatic water?
Only for a single-use preparation. Sterile water has no preservative and is not designed to be re-entered, so it is the wrong choice when you need to draw from the same vial more than once.
Is distilled water the same as sterile water?
No. Distilled water is purified by distillation but is not guaranteed to be sterile or injection-grade. Sterile water is specifically sterilized and tested for that purpose.
Why does bacteriostatic water last longer once opened?
Because the 0.9% benzyl alcohol continuously inhibits bacterial growth, an opened multi-dose vial stays usable for roughly 28 days when stored and handled per protocol, whereas preservative-free sterile water is discarded after one entry.