How long does bac water last after opening?
How long does bac water last is really two questions: how long the unopened vial keeps, and how long you have after opening it. The short answers are above. Here's the detail, with the refrigeration question people always ask, each point tied to the official label.
Unopened vs opened: two different timelines
| Unopened vial | Keeps until the manufacturer's printed expiry date, stored correctly |
|---|---|
| After first puncture | Commonly used within about 28 days, then discarded (USP <797> practice, not a label figure)4 |
| Why the limit exists | The benzyl alcohol preservative holds back bacterial growth for a limited period once the vial is entered1 |
The preservative is the whole reason bac water is a multi-dose product in the first place. It's what lets you draw from the vial more than once, and it's also what sets the clock running once you open it.1
Do you refrigerate bac water?
No. The label specifies controlled room temperature, 20 to 25 °C (68 to 77 °F), and carries no refrigeration instruction.3 So a fridge isn't needed. Keep the vial in its packaging and use aseptic technique every time you enter it.2
How to store bac water
Storage is simple, and getting it right is what protects the 28-day window:
- Keep it at controlled room temperature, 20 to 25 °C, per the label.3
- Leave the seal intact until you're ready to use it.2
- Wipe the stopper and use aseptic technique on every withdrawal.2
- Note the date you first opened it, so you can track the ~28-day in-use window.
When to throw it out
Discard the vial once you reach the end of the after-opening window, or sooner if anything looks off. The label is clear on one point: don't use the product unless the solution is clear and the seal is intact.2 Cloudiness, particles, discoloration, or a compromised seal all mean it goes in the bin.
From the label. Bac water is for drug-diluent use only and is not for use in neonates, because of the potential toxicity of benzyl alcohol.2 Always follow a healthcare professional's guidance and the drug manufacturer's instructions.
Frequently asked questions
How long is bac water good for after opening?
Commonly about 28 days after the first puncture (USP <797> practice), then it's discarded.4
Does bac water expire?
Yes. Unopened, it has a printed manufacturer expiry date. Opened, the after-puncture window applies regardless of that date.2
Should bac water be refrigerated?
No. The label specifies controlled room temperature, 20 to 25 °C, and gives no refrigeration instruction.3
Can I use bac water after 28 days?
The after-opening window exists because the preservative's protection is time-limited, so an opened vial is discarded at the end of it rather than kept longer.1,2
What is bac water? Bac water 30 mL
- Bacteriostatic Water for Injection, USP — Description (preservative and multiple-dose use). DailyMed, U.S. National Library of Medicine. View label.
- Bacteriostatic Water for Injection, USP — Directions, Warnings & Precautions (aseptic use; clear-and-sealed; neonate warning). DailyMed. View label.
- Bacteriostatic Water for Injection, USP — Storage, 20–25 °C (Hospira, Inc.). DailyMed. View document.
- Beyond-use dating for preserved multiple-dose containers (28-day in-use window). USP General Chapter <797> Pharmaceutical Compounding — Sterile Preparations. (Standard pharmacy practice; the manufacturer label sets no in-use discard date.) USP <797>.