How Long Does Bacteriostatic Water Last After Opening?
By the BacWaterPep editorial team · Updated
Short answer. An opened vial of bacteriostatic water is generally discarded 28 days after the first puncture, unless its label gives a different date (CDC). Unopened, it keeps until the expiry printed on the vial when stored at controlled room temperature, protected from light and not frozen.
| After first puncture | 28 days (or the label's date) |
|---|---|
| Unopened | Until the expiry on the vial / COA |
| Storage | 15–25 °C, protected from light, do not freeze (our specification) |
| Discard immediately if | Cloudy, particles, damaged stopper, or sterility in doubt |
Mark the date
Write the date of first puncture on the vial. The 28-day period runs from that day, not from purchase.
Buy the size you will finish
A 30 mL vial used at 5 mL a month means 25 mL in the bin every month. Match the vial to 28 days of use; our sister shop's Size Finder does the arithmetic.
What 28 days does not mean
- It is not a stability claim for anything you dissolve in the water.
- It does not make a contaminated vial safe — the preservative inhibits, it does not sterilise.
- It does not extend an expired vial.
Storage in transit
Bacteriostatic water is stored at room temperature. Avoid freezing and prolonged heat; inspect vials on arrival.
Sources
- CDC — Preventing Unsafe Injection Practices (multi-dose vials, 28-day rule)
- DailyMed — Bacteriostatic Water for Injection, USP (0.9% benzyl alcohol), Hospira label
Buying by the box? See box prices or request a quote.