BAC Water vs Saline
Plain saline is salt water (0.9% sodium chloride). It has no preservative, so like sterile water it is one-time use once opened. BAC water adds benzyl alcohol (a germ-fighting preservative) that fights germs across many draws. For peptides you use over time, BAC water is the standard choice.
| Bac water | Saline | |
|---|---|---|
| Contents | Sterile water plus 0.9% benzyl alcohol | 0.9% sodium chloride in water |
| Preservative | Yes | No (plain saline) |
| Multi-dose safe | Yes | No (plain saline) |
| Best for | Peptide reconstitution over days or weeks | Single-use rinsing or dilution |
Preservative, not salt, is the point
For mixing peptides, the key difference is the preservative, not the salt. Plain saline has no preservative. Once you open a vial, use it one time only. BAC water keeps a vial safe to use many times. That is why it is the go-to for peptides used over time.
A note on preserved saline
There is also a preserved saline (0.9% saline with benzyl alcohol added). It acts more like BAC water. If your saline is preserved, check the label for benzyl alcohol. Plain saline is the common kind, and it is not preserved.
BAC Water vs Saline: common questions
More bac water comparisons
Reconstitute a specific peptide
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.
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