Bacteriostatic vs. Sterile Water

Both bacteriostatic water and sterile water look identical, but they behave very differently once a peptide is reconstituted.

Sterile water for injection

Contains only water, sterilized. It has no preservative, so a reconstituted vial must be used immediately (typically discarded within 24 hours) because bacteria can proliferate once the seal is breached.

Bacteriostatic water

Contains 0.9% benzyl alcohol, which inhibits bacterial growth. This allows a reconstituted vial to be stored refrigerated and used over multiple doses — commonly up to 30 days.

Recommendation for researchers

For multi-dose research use, bacteriostatic water is the standard diluent because it extends the usable life of a reconstituted peptide vial and reduces waste.