Vial Shelf Life

Also known as: shelf life · vial expiration

Vial shelf life ends at the earlier of the original expiration date and the applicable limit after opening or mixing.

A vial has more than one clock. The expiration date covers the unopened product stored as directed, and it comes from the manufacturer's stability testing. Once a vial is punctured, or a powder is mixed with liquid, a separate in-use limit applies. For opened multi-dose vials in health care, the CDC, citing USP General Chapter <797>, says to date the vial and discard it within 28 days unless the manufacturer states a different date. The beyond-use date must never exceed the manufacturer's original expiration date.

For a mixed peptide, the in-use limit is specific to the product. The approved tesamorelin product EGRIFTA WR, for example, is reconstituted with bacteriostatic water, stored at room temperature, must not be refrigerated or frozen after mixing, and is discarded 7 days after mixing. The bacteriostatic water bottle used to mix it has its own 28-day limit. After opening or mixing, use the earlier of the original expiration date and the applicable in-use limit.

Why it matters

The 28-day figure is about opened multi-dose containers, mainly a contamination limit. It is not a stability rating for a peptide you mixed yourself. The bacteriostatic water label says reconstituted solutions should not be stored unless the drug's manufacturer says they can be.

For most research peptides there is no manufacturer-tested in-use period, so how long a mixed vial keeps its potency is not known. Stability is specific to each compound and formulation. Claims such as 'good for 30 to 60 days in the fridge' are not backed by published testing for most of these products.

How to track it

Note the expiration date and storage conditions of each sealed vial.
Write the mix date (and first-puncture date) on every vial you open.
Follow the manufacturer's in-use limit if one exists and discard by the earlier of that limit and the original expiration date; if none exists, mix smaller amounts so each vial is used up sooner and never use it after expiry.
Discard any vial whose solution becomes cloudy, discolored or develops particles.
Discard opened multi-dose diluent bottles by the earlier of their original expiration date and their in-use limit (28 days after first puncture unless the manufacturer specifies a different limit).

Draws per vial = vial mcg ÷ dose mcg

Worked example

A 5 mg vial holds 5 × 1000 = 5000 mcg. At 250 mcg per draw that is 5000 ÷ 250 = 20 draws, before allowing for liquid lost in the syringe and vial. At one draw a day, the vial is open for about 20 days. The number of draws does not extend either time limit. If EGRIFTA WR is mixed 2 days before its original expiration date, discard it at that expiration date, after at most 2 days, rather than waiting for its 7-day post-mixing limit.

Common mistakes

Treating the 28-day multi-dose rule as proof a mixed peptide stays potent for 28 days.
Not writing the mix date on the vial.
Assuming refrigeration is always correct; some approved peptide products must not be refrigerated after mixing.
Reconstituting a large vial for a small dose so it sits open far longer than any tested period.
Using a solution that has changed color or clarity.

Sources

GuidelinePreventing Unsafe Injection Practices. Centers for Disease Control and Prevention, 2024.
Prescribing informationEGRIFTA WR (tesamorelin) for injection - prescribing information and instructions for use. DailyMed, U.S. National Library of Medicine, 2025.
Prescribing informationBacteriostatic Water for Injection, USP (Hospira) - prescribing information. DailyMed, U.S. National Library of Medicine, 2019.

Page updated October 3, 2026. How we grade evidence: methodology.

Related Terms

BAC Water

Bacteriostatic water (BAC water) is sterile water for injection with 0.9% benzyl alcohol added as a preservative, used to dissolve drugs for injection.

Reconstitution

Reconstitution is dissolving a freeze-dried (lyophilized) powder in a measured volume of liquid to make a solution of known concentration for injection.

Cold Chain

Cold chain is the unbroken control of temperature for a temperature-sensitive product, from manufacture through shipping and storage to use.

Lyophilization

Lyophilization (freeze-drying) removes water from a frozen product under vacuum, leaving a dry powder or cake that is more stable than a solution.

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