Bacteriostatic Water vs Sterile Water for Peptide Research
Sterile water and bacteriostatic water look identical in the vial. The difference is one ingredient, and it changes how long an opened vial can be kept.
By Morry Mason · Updated · How we checkWe may earn a commission from some links on this page. Disclosure
Bacteriostatic water is sterile water plus 0.9% benzyl alcohol, a preservative, so the vial can be entered more than once. Plain sterile water has no preservative. Its label says it comes in single-use containers and the unused portion is discarded.
Side by side
| Point | Bacteriostatic water | Sterile water |
|---|---|---|
| Preservative | 0.9% benzyl alcohol (some licensed vials 1.1%) | None: no bacteriostat or antimicrobial agent |
| Entries per vial | Single or repeat entry, per the Hospira label | Single-use containers only |
| After opening | Commonly dated and discarded within 28 days, unless the maker states otherwise | Discard the unused portion |
| Common lab sizes | 10 mL and 30 mL vials | Varies by maker |
Sources: bacteriostatic water label (Hospira) on DailyMed, sterile water label (Hospira) on DailyMed and CDC clinical safety guidance for multi-use vials (cdc.gov), checked 5 Nov 2026.
Sterile water for peptides: what to check on the listing
Whichever you buy for the lab, the listing should state exactly what is in the vial. For bac water that means 0.9% benzyl alcohol. For sterile water it means no additives. Many research supply listings call both "water", so read the contents line, not the title.
- Contents stated in full, including the preservative and its strength.
- Fill volume in mL, so you can work out the price per mL.
- A lot report for the water itself, with sterility and endotoxin results.
The FDA drug shortages list showed sterile water products in shortage on 5 Nov 2026. That affects licensed supply, not research suppliers.
A bac water with a full lot report
More options are on the sizes and price per mL page.
Quick answers
Is sterile water the same as bacteriostatic water?
No. Both are sterile water, but bacteriostatic water has 0.9% benzyl alcohol added as a preservative. Plain sterile water has none.
Can a sterile water vial be opened more than once?
The Hospira sterile water label says it is supplied only in single-use containers and to discard the unused portion.
Why does bac water last longer once opened?
The benzyl alcohol is a preservative that holds back bacterial growth. That is why the vial can be entered more than once, within the time limits set out on our storage page.
Sources
- bacteriostatic water label (Hospira) on DailyMed, checked Nov 5, 2026
- sterile water label (Hospira) on DailyMed, checked Nov 5, 2026
- CDC clinical safety guidance for multi-use vials (cdc.gov), checked Nov 5, 2026
- FDA drug shortages list, checked Nov 5, 2026
- pspeptides.com product page, checked Nov 5, 2026
Research suppliers list 10 mL and 30 mL vials from $0.50 to $1.60 per mL.
Compare price per mLOur pick
PSPeptides 10 mL, with a lot report covering sterility, endotoxin and a fentanyl screen.
View on PSPeptides