For informational purposes only. Not medical advice. Consult a licensed healthcare provider.
The Short Answer
Bacteriostatic water contains 0.9% benzyl alcohol as a preservative. Sterile water does not. This single difference determines whether a vial can be used for multiple draws or must be discarded after one use.
Bacteriostatic Water
Bacteriostatic water (BAC water) is sterile water for injection with 0.9% benzyl alcohol added as a bacteriostatic agent. The benzyl alcohol inhibits bacterial growth, allowing the water - and any solution reconstituted with it - to remain safe for multiple punctures over a period of up to 28 days.
Key characteristics:
- Multi-use vial (up to 28 days after first puncture)
- Contains 0.9% benzyl alcohol preservative
- USP-grade when sourced from FDA-registered facilities
- Shelf life: 24 months sealed
- Stored at room temperature
Sterile Water for Injection
Sterile water for injection (SWFI) is purified water that has been sterilized and contains no preservatives, antimicrobial agents, or added buffers. Once the vial is punctured, there is no mechanism to prevent bacterial contamination.
Key characteristics:
- Single-use only - discard after one puncture
- No preservatives
- Required for certain IV preparations
- Required for neonatal applications (benzyl alcohol contraindicated)
When to Use Each
| Use Case | BAC Water | Sterile Water |
|---|---|---|
| Multi-dose reconstitution | Yes | No |
| Subcutaneous injection | Yes | Yes |
| IV administration | No | Yes |
| Neonatal use | No | Yes |
| Multi-day protocols | Yes | No |
Why BAC Water is Standard for Reconstitution
For most reconstitution applications, bacteriostatic water is the standard choice because:
- Multi-draw safety - The benzyl alcohol prevents bacterial growth between uses
- Cost efficiency - One vial serves multiple doses over 28 days
- Convenience - No need to discard and open a new vial for each use
- Stability - The preservative helps maintain solution integrity
Sterile water is only preferred when the preservative is contraindicated - primarily IV preparations and neonatal applications.
Quality Matters
Not all bacteriostatic water is created equal. The FDA has noted that many products sold online fail basic quality testing for pH, benzyl alcohol concentration, and sterility. Always source from vendors who provide Certificates of Analysis from accredited third-party laboratories and who source from FDA-registered 503B outsourcing facilities.
View our Certificates of Analysis for every batch we sell.