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Storage

How Long Does Bac Water Last, and Does It Need a Fridge?

Storage questions about bac water come down to three things: the temperature before opening, the 28-day window after, and the expiry date on the vial. This page covers the diluent only.

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Quick answer

Unopened bac water is stored at room temperature, 20 to 25°C (68 to 77°F), per the Hospira label. Once a vial is first entered, the common rule is to date it and discard it within 28 days unless the maker states another date.

Before opening

  • Temperature: Store at 20 to 25°C (68 to 77°F), per the bacteriostatic water label (Hospira) on DailyMed.
  • Refrigeration: not required before opening, according to the PSPeptides product page.
  • Light and freezing: PSPeptides says to keep it away from direct sunlight and to avoid freezing.
  • Shelf life: the expiry date printed on the vial. We did not find a general shelf life in years on the label.

After first opening: the 28-day rule

The Hospira label does not state a discard period in days. The 28-day figure comes from CDC guidance for multi-use vials: they should be "dated and discarded within 28 days unless the manufacturer states another date." PSPeptides gives the same window on its product page: use within 28 days of first puncture.

Simple lab habit: write the date of first opening on the vial or in the lab log, along with the lot number.

When to discard a vial early

  • The liquid is cloudy, discolored or has particles in it (PSPeptides product page).
  • The expiry date has passed.
  • The seal or cap was damaged on arrival.

Does vial size matter for storage?

The 28-day window runs from first opening, whatever the size. A larger vial is cheaper per mL, but only if the lab uses it within the window. See bac water sizes and price per mL.

4 questions

Quick answers

Does bac water need to be refrigerated?

Not before opening. The Hospira label says to store it at 20 to 25°C (68 to 77°F), and PSPeptides says refrigeration is not required before opening.

How long does bac water last once opened?

The common rule is to date the vial when first entered and discard it within 28 days, unless the maker states another date. That rule comes from CDC guidance for multi-use vials.

How long does an unopened vial last?

Until the expiry date printed on the vial. Check it when the order arrives.

Can bac water be frozen?

PSPeptides says freezing should be avoided. The Hospira label gives a room temperature range only.

Sources

  1. bacteriostatic water label (Hospira) on DailyMed, checked Nov 5, 2026
  2. CDC clinical safety guidance for multi-use vials (cdc.gov), checked Nov 5, 2026
  3. pspeptides.com product page, checked Nov 5, 2026
At a glance

Research suppliers list 10 mL and 30 mL vials from $0.50 to $1.60 per mL.

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Our pick

PSPeptides 10 mL, with a lot report covering sterility, endotoxin and a fentanyl screen.

View on PSPeptides

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