How Long Does Bacteriostatic Water Last? Shelf Life and Storage
Unopened, bacteriostatic water lasts until the expiration date printed on the vial. Once the stopper is first punctured, the usual convention for a multiple-draw vial is to discard it within 28 days unless the manufacturer states otherwise, and never after the printed expiry. The FDA-labeled product is stored at 20 to 25°C (68 to 77°F), so it does not need refrigeration. Keep vials upright, sealed, and away from light.
Bacteriostatic water is sterile water with 0.9% benzyl alcohol added as a preservative, supplied in a vial that is meant to be entered more than once [1]. Two dates control how long a vial stays usable: the expiration date the manufacturer prints on the label, and a beyond-use date that starts the first time the stopper is punctured [2, 3]. This guide explains both, the storage conditions on the FDA-labeled product, and a simple way to track vials in a lab.
The FDA-labeled versions of bacteriostatic water are prescription-only products [1, 5]. Batch reconstitution solution is supplied for laboratory and research use only, and the label figures below are cited as a published reference point, not as claims about Batch.
How long does unopened bacteriostatic water last?
An unopened vial is good until the expiration date on its label, provided it has been stored as labeled [3]. There is no single shelf life for all bacteriostatic water: each manufacturer sets its own expiry from its stability data, so read the date on the vial or carton rather than relying on a general rule. CDC handling guidance for multiple-draw vials says an unopened vial should be discarded according to the manufacturer's expiration date [3].
Batch supplies a Certificate of Analysis for every batch, so record the lot number of each vial when it arrives. See how to read a Certificate of Analysis for what each field means.
How long does bacteriostatic water last after opening?
The common answer is 28 days after first puncture. That figure is a default, not a property of the liquid. FDA guidance on container labeling states that the beyond-use date for an opened or entered (for example, needle-punctured) multiple-draw container is 28 days unless the manufacturer specifies otherwise on the label, and that such containers usually carry no separate discard statement because 28 days is assumed [2]. The same guidance traces the convention to USP General Chapter <659>, Packaging and Storage Requirements [2].
CDC handling guidance for multiple-draw vials, which cites USP General Chapter <797>, gives the same rule: once a vial is opened or punctured it should be dated and discarded within 28 days unless the manufacturer states another date, and the beyond-use date should never exceed the manufacturer's original expiration date [3]. In practice, use whichever comes first: 28 days from first puncture, or the printed expiry.
The benzyl alcohol preservative is the reason a vial can be entered repeatedly, but CDC notes that the preservative does not provide complete protection against bacterial contamination [3]. Aseptic technique at each entry matters as much as the calendar.
What is the storage temperature for bacteriostatic water?
The FDA-labeled product is labeled "Store at 20 to 25°C (68 to 77°F)" with a reference to USP controlled room temperature [1, 5]. USP currently defines controlled room temperature as 20 to 25°C, with excursions permitted between 15 and 30°C [4]. USP has published a proposal to revise that definition to 15 to 25°C to align with other pharmacopeias, so check the current text if your SOPs quote it [4].
Batch's product specification lists storage as room temperature, away from light. A climate-controlled lab bench, cabinet, or storeroom is usually suitable; avoid spots near ovens, autoclaves, sunny windows, or HVAC vents where temperatures swing.
Does bac water need to be refrigerated?
No. The labeled storage condition for the FDA-labeled product is controlled room temperature, not refrigeration [1]. Refrigerator temperatures fall below the 15°C lower limit of the permitted excursion range [4], so refrigeration is not a way to extend shelf life or the 28-day window. Follow the label on the vial you have.
Can bacteriostatic water be frozen, and does light matter?
The FDA-labeled product's label gives a storage temperature range but no separate freezing or light instruction [1]. Freezing takes a vial far outside the labeled 20 to 25°C range [1], so treat a vial that has frozen as stored outside its labeled conditions and set it aside rather than relying on it. For light, Batch's specification calls for storage away from light; keeping vials in their carton or a closed cabinet meets that.
How should a lab record the first-puncture date?
CDC guidance says an opened multiple-draw vial should be dated [3]. A simple, auditable method:
- At first puncture, write the date (and initials) on the vial label or a pre-printed sticker.
- Write the discard date next to it: first-puncture date plus 28 days, or the printed expiry if that is sooner [2, 3].
- Log the lot number, open date, and discard date in your inventory sheet or LIMS so the vial can be traced to its Certificate of Analysis.
- Before each use, check the discard date and inspect the solution; the label says not to use it unless the solution is clear and the seal intact [1].
- Discard any vial whose sterility is compromised or questionable, whatever the date [3].
Vial size affects waste. If a project only needs a few millilitres over a month, a 3 mL vial (sold in packs of ten) is less likely to reach day 28 with liquid left than a 10 mL vial. See bacteriostatic water vial sizes for a fuller comparison.
Bacteriostatic water storage checklist
| Check | What to look for | Basis |
|---|---|---|
| Expiration date | Printed expiry not yet passed | Manufacturer's expiration date governs unopened vials [3] |
| Storage temperature | Kept at 20 to 25°C; brief excursions only within 15 to 30°C | Label storage statement and USP controlled room temperature [1, 4] |
| Refrigeration | Not required; store at room temperature | Labeled storage condition [1] |
| Light | In carton or closed cabinet | Batch specification: away from light |
| First-puncture date | Written on vial and in log | Opened vials should be dated [3] |
| 28-day window | Within 28 days of first puncture, unless the label states otherwise | FDA labeling guidance and CDC handling guidance [2, 3] |
| Appearance and seal | Solution clear; seal intact | Label: do not use unless clear and seal intact [1] |
| Sterility doubt | Any reason to suspect contamination means discard | CDC handling guidance [3] |
Key takeaways
- Unopened vials last until the printed expiration date; there is no universal shelf life [3].
- After first puncture, the default beyond-use date is 28 days unless the manufacturer states otherwise, and never past the printed expiry [2, 3].
- The FDA-labeled product is stored at 20 to 25°C (68 to 77°F); it does not need refrigeration [1].
- Date every vial at first puncture and log the lot number.
- Discard any vial that is cloudy, has a broken seal, or may be contaminated [1, 3].
For how Batch documents each lot, see how Batch tests and documents each batch. For what a good vial should look like, see is bacteriostatic water supposed to be clear?.
Frequently asked questions
Where does the 28-day rule come from?
It is the default beyond-use date for opened multiple-draw containers in FDA labeling guidance, which cites USP General Chapter <659> [2]. CDC handling guidance repeats it and cites USP <797> [3]. A manufacturer can set a different date on its label if it has data to support it [2].
Is bacteriostatic water still usable after the expiration date?
Don't rely on it. The beyond-use date for an opened vial should never exceed the original expiration date, and unopened vials should be discarded according to that date [3].
Does an unopened vial have a 28-day limit?
No. The 28-day clock starts when the vial is first opened or punctured; until then the printed expiration date applies [2, 3].
What if a vial was left in a hot car or shipped in summer?
USP controlled room temperature allows brief excursions up to 30°C [4]. If you suspect a vial went well beyond that, contact Batch support with the lot number before using it. Our shipping and packaging policy covers how orders are packed.
For laboratory and research use only. Not for human or veterinary use. Not intended to diagnose, treat, cure, or prevent any disease.
Sources
- BACTERIOSTATIC WATER injection, solution (Hospira, Inc.) — label — DailyMed, U.S. National Library of Medicine. Accessed October 24, 2026.
- Selection of the Appropriate Package Type Terms and Recommendations for Labeling Injectable Medical Products Packaged in Multiple-Dose, Single-Dose, and Single-Patient-Use Containers for Human Use (Guidance for Industry, October 2018) — U.S. Food and Drug Administration. Accessed October 24, 2026.
- Preventing Unsafe Injection Practices — Centers for Disease Control and Prevention. Accessed October 24, 2026.
- 〈659〉 Packaging and Storage Requirements (revision briefing) — United States Pharmacopeia. Accessed October 24, 2026.
- Bacteriostatic Water for Injection, USP — prescribing information — Pfizer (Hospira). Accessed October 24, 2026.