If you've reconstituted a lyophilised research peptide, you've almost certainly used bacteriostatic water. It's the quiet workhorse of the process — but it's often misunderstood, and it's not interchangeable with every other kind of water. Here's what it is and why it's the standard choice.

The simple definition

Bacteriostatic water is sterile water with 0.9% benzyl alcohol added as a preservative. The benzyl alcohol is bacteriostatic — it inhibits the growth of bacteria rather than killing them outright — which is where the name comes from. That single additive is what sets it apart from plain sterile water.

Why the preservative matters

The benzyl alcohol is what allows a reconstituted vial to be drawn from more than once over a period of time. Without a bacteriostatic agent, once you break the seal and introduce it to the environment, any solution is a one-use proposition. With it, the solution resists microbial growth, so a multi-draw vial stays usable across the preservative's effective window (typically around 28 days once opened, though this varies).

Bacteriostatic vs sterile vs distilled water

  • Bacteriostatic water — sterile water + benzyl alcohol. Best for reconstituting peptides you'll draw from over several sessions. The standard research choice.
  • Sterile water for injection — sterile, but no preservative. Suitable where the entire reconstituted amount is used in one go, immediately.
  • Distilled water — purified of minerals but not necessarily sterile, and no preservative. Not appropriate as a peptide diluent for research where sterility and shelf life matter.

For most research peptide work, where a vial is reconstituted and then drawn from across a number of sessions, bacteriostatic water is the sensible default.

How to store it

Unopened bacteriostatic water is stable at room temperature — keep it out of direct light. Once opened, note the date; its effective bacteriostatic period runs from first use. It doesn't need refrigeration, but the reconstituted peptide made with it usually does. For the full process, see our guide on storing and reconstituting research peptides.

Where to get it

Because it's needed for nearly every lyophilised peptide, we stock bacteriostatic water alongside the range so you can reconstitute straight away rather than sourcing it separately. It ships from the same Australian stock, same or next business day dispatch.

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All products are supplied strictly for laboratory and in-vitro research use only. Not for human or veterinary consumption. This article is general information about laboratory supplies and is not medical or veterinary advice.