Stability data · 120 days · three vials
How long does bacteriostatic water actually hold?
Bacteriostatic water is sterile water with 0.9% benzyl alcohol as the bacteriostatic agent. The question that matters is how long that agent stays where it should be once the stopper has been punctured. Three vials were tracked for 120 days — one left alone, one drawn from every week, one refrigerated.
Testing punctures only
0.816
at day 120, from 0.883
Weekly draws + testing
0.817
at day 120, from 0.892
Weekly draws + testing
0.844
at day 120, from 0.888
Vial 01 — room temperature, testing punctures only
| Day | 0 | 30 | 60 | 90 | 120 |
|---|---|---|---|---|---|
| Reading | 0.883 | 0.918 | 0.894 | 0.898 | 0.816 |
Vial 02 — room temperature, weekly draws + testing
| Day | 0 | 30 | 60 | 90 | 120 |
|---|---|---|---|---|---|
| Reading | 0.892 | 0.895 | 0.893 | 0.890 | 0.817 |
Vial 03 — refrigerated, weekly draws + testing
| Day | 0 | 30 | 60 | 90 | 120 |
|---|---|---|---|---|---|
| Reading | 0.888 | 0.904 | 0.911 | 0.899 | 0.844 |
All three vials together
What the numbers say
Puncture count was not the driver
The vial drawn from every week for four months finished at 0.817. The vial opened only for scheduled testing finished at 0.816. Roughly seventeen extra punctures produced no measurable difference — which is notable, because puncture count is what most people worry about.
Time was the driver
All three conditions held a narrow band from day 0 through day 90, then stepped down together between day 90 and day 120 — a fall of roughly 8% from baseline in both room-temperature vials.
Cold storage helped, modestly
The refrigerated vial ended at 0.844 against 0.816 and 0.817, keeping about a third of what the others lost. Real, but not transformative.
The practical read
Through 90 days, handling barely mattered. Past 90 days, everything drifted regardless of how carefully it was treated. If consistency matters to your work, plan around the calendar rather than around how many times you have entered the vial — and keep it cold if it is going to sit.
What this study is not
One vial per condition, five measurements each, a single run with no error bars. The units are not stated clearly in the report, so every chart here uses the report's own 0.75-1.00 detail scale with no unit claimed. Read the shape of the curves as the finding, not the absolute figures. Testing: BioInfinity / Verum Lab.
Questions
How long does bacteriostatic water last after opening?
In this 120-day study all three vials held a narrow band of readings from day 0 through day 90, then stepped down together between day 90 and day 120 — about 8% below baseline for both room-temperature vials. Time, not handling, was what moved the numbers.
Do repeated punctures degrade bacteriostatic water?
Not measurably here. The vial drawn from every week for four months finished at 0.817, while the vial opened only for scheduled testing finished at 0.816 — roughly seventeen extra punctures made no difference to the benzyl alcohol reading.
Should bacteriostatic water be refrigerated?
Refrigeration helped modestly. The cold vial ended at 0.844 versus 0.816 and 0.817 for the two room-temperature vials, retaining roughly a third of what the others lost. Worthwhile if a vial is going to sit for months, not transformative.
What is the 28-day rule for bacteriostatic water?
The 28-day figure comes from clinical convention for multi-dose vials, not from a stability measurement of the preservative itself. This study measured the benzyl alcohol content rather than sterility, and found it steady through 90 days under both careful and heavy handling.
What are the limits of this study?
One vial per condition, five measurement points each, a single run with no error bars. The units are not stated clearly in the report, so every chart is plotted on the report's own 0.75-1.00 detail scale with no unit claimed. Read the shape of the curves as the finding rather than the absolute values.
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Bacteriostatic Water — 30ml, 0.9% benzyl alcohol
Sterile, sealed vial with the certificate available for your lot. Held in our own US facility and dispatched the same business day before 3pm ET.
Supplied for in-vitro laboratory research only. Not a drug, supplement or medical device. Not for human or veterinary use.