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Unopened vials: Store at controlled room temperature (20-25 degrees C / 68-77 degrees F) Protected from light in original packaging Good until manufacturer-printed expiration date (typically 18-24 months from production) Do not freeze freezing can compromise the glass vial seal and alter preservative distribution After first puncture: Refrigerate at 2-8 degrees C (36-46 degrees F) 28-day use window from first needle puncture per Pfizer/Hospira prescribing information Swab the rubber stopper with 70% isopropyl alcohol before every puncture Label the vial with the first-puncture date Discard after 28 days regardless of remaining volume or visual appearance What shortens the 28-day window: Room-temperature storage after puncture (can reduce effective window to 7-10 days) Excessive puncture count (30+ punctures accelerate preservative depletion) Poor aseptic technique (skipping alcohol swabs introduces surface contamination) Temperature cycling (moving between fridge and room temp repeatedly) For a deep dive on shelf life, degradation signs, and the science behind the 28-day rule, see How Long Does Bac Water Last After Opening

Once supplementation stops, B12 levels typically return to the normal range within a few months
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This inhibits the growth of bacteria in the water for up to 28 days after first use
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