How long does BAC water last?
Unopened BAC water lasts until the expiry date printed by the manufacturer. Once a multi-dose vial is opened, CDC guidance is to date it and discard it within 28 days unless the manufacturer specifies another opened-vial period, and never beyond the printed expiry. A peptide mixed with that water follows its own product instructions, not the water's dates.
Sources checked September 29, 2026. General reference, not a medical review or product-specific instruction.
Three different dates
| Container | How long it lasts | Where the date comes from |
|---|---|---|
| Unopened BAC water | Until the printed manufacturer expiry | That water product's label |
| Opened multi-dose vial | 28 days from first puncture (CDC), unless the manufacturer states otherwise; never past expiry | CDC guidance and manufacturer instructions |
| Reconstituted product | Set by the exact product's instructions | Product-specific instructions |
How long does unopened BAC water last?
Until the expiry date printed by the manufacturer, when stored as the label directs. Pfizer's Bacteriostatic Water for Injection label specifies storage at 20 to 25°C (68 to 77°F). The printed date is the limit; nothing on this site extends it.
How long does BAC water last after opening?
CDC guidance for an opened multi-dose vial is to date it when first punctured and discard it within 28 days, unless the manufacturer specifies a different opened-vial period, and never beyond the printed expiry. Write the opening date on the vial.
Does BAC water need to be refrigerated?
Do not assume it does. Pfizer's label specifies 20 to 25°C (68 to 77°F), which is controlled room temperature, not a refrigerator. Follow the exact label for the product you have. Once a substance is added, that product's storage instructions govern the mixture.
Can BAC water be stored at room temperature?
For the Pfizer product, controlled room temperature is the labeled storage condition: 20 to 25°C (68 to 77°F). Keep the container closed and protected as the label directs, and check the container itself, because other manufacturers can state different conditions.
Can you freeze BAC water?
The label specifies 20 to 25°C and gives no instruction for frozen storage, so freezing is outside the labeled range. A container that has been frozen should be treated as a deviation from the label: ask the dispensing pharmacist or manufacturer rather than assuming it is usable.
Does BAC water expire, and can you use it past 28 days?
Yes. CDC guidance is to discard an opened multi-dose vial within 28 days unless the manufacturer states another opened-vial date, and never beyond the printed expiry. This site cannot assess an expired or long-opened container; questionable sterility is a reason to discard a vial even before its dated limit.
How long does a reconstituted peptide last?
That depends on the exact product and formulation, not on the water. The water's expiry and the 28-day opened-vial guidance do not transfer to a mixture. Use the storage and discard instructions for the specific product, and record the mix date separately from any calculation.
What the 28-day guidance does not mean
CDC's opened multi-dose guidance does not certify that a mixed solution remains stable for 28 days. Preservative also does not provide complete protection against contamination. Questionable sterility is a reason to discard a vial, even before its dated limit.
A clear-looking solution, a calendar reminder or a correct concentration calculation is not a test of sterility or potency. For medication-specific questions, ask the dispensing pharmacist or prescriber.
What can the calculator tell you?
It converts entered amounts and volumes. For example, 10 mg in a final volume of 2 mL is 5 mg/mL. Neither that arithmetic nor a compound name establishes an expiry date.
Saved calculations and printed labels keep the calculation separate from product-specific storage instructions. They do not generate a safe-use date. See what no calculation can verify, what a product's storage instructions must state and the vial-label tool.
References
Primary sources for the facts on this page. We cite regulatory and peer-reviewed authorities rather than secondary blogs.
- Bacteriostatic Water for Injection, USP: product labeling · Pfizer MedicalStorage temperature for this specific product and product-specific dilution instructions.
- Preventing Unsafe Injection Practices: multi-dose vials · CDCOpened-vial dating, manufacturer exceptions and contamination limitations.
Record the opening date, then check the math
Print a small label with your mix date and concentration, or check the numbers from your existing instructions. Keep the product label alongside either.