Bacteriostatic water vs sterile water: which one for mixing?
Quick answer
Bacteriostatic water is sterile water with 0.9% benzyl alcohol added, so an opened bac water vial is good for about 28 days; sterile water is single-use. The alcohol stops bacteria multiplying in the bottle once it has been opened. If you will draw from the mixed vial more than once, you want bacteriostatic water. Neither is saline, and neither is tap or bottled water.
Side by side
Rows that differ are highlighted. Values come from the product records for the two products named in the header.
Bacteriostatic water Bac Water (Bacteriostatic Water), 30 mL |
Sterile water Sterile Water for Injection |
|
|---|---|---|
| LiquidLiquid is what the bottle holds. Bacteriostatic water has a preservative and keeps 28 days once opened; sterile water and saline have none and are single-use. Glossary | Bacteriostatic water | Sterile water |
| PreservativePreservative says whether it carries one: 0.9% benzyl alcohol stops bacteria multiplying in an opened bottle, and it is what makes a multi-dose bottle possible. Glossary | Yes | No |
| Volume | 30 mL | 10 mL |
| Single-use | No | Yes |
| Once openedOnce opened is how long the bottle is considered good after the first needle goes through the stopper. | 28 days | 0 days |
| PricePrice tier is the rough position within its category, not a live price: budget is the cheapest sensible option, premium costs more for a reason the page explains. | Budget | Budget |
| TravelTravel says whether it is practical to fly with: carry-on means it goes through security without fuss. | Carry-on friendly | Carry-on friendly |
| SterileSterile means individually sealed and sterile until opened; anything that touches the inside of a vial or your skin should be. | Yes | Yes |
| PackPack is how many come in the listing this site links to; it is shown only where every store's listing gives the same count. Check it against the listing, since photos often show ten and ship one. | 1 | 1 |
| Reusable | No | No |
Which should you choose?
- Pick bacteriostatic water for anything you will draw from over days or weeks. This is the everyday choice.
- Pick sterile water only for a vial you will use all at once, or where the product's own instructions say benzyl alcohol is not wanted.
- Saline is the usual choice for nasal sprays; bac water is the preserved alternative.
The products
Open in the comparison tool Find the right mixing water
Related guides
- Bac water vs sterile water vs saline (and which to buy)
- How long does bac water last once opened?
- Cloudy vials and reconstitution mistakes: what went wrong, and what can be saved
Common questions
Can I use sterile water instead of bacteriostatic water?
For a single use, yes. For a vial you keep, no: nothing stops bacteria growing in it.
How long does bacteriostatic water last once opened?
About 28 days; write the date on the vial.
Is saline the same as sterile water?
No. Saline is 0.9% salt in water, used for nasal preparations; sterile water has nothing in it.
Last edited . Equipment only: nothing on this page is advice about what to inject, how much, or whether a product is fit to use. That comes from the product's labelling and whoever supplied it. Product pages link to your own country's Amazon store through affiliate links; your price is the same.