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Is my mixed peptide vial still good?
The one general limit a source gives is 28 days: the CDC's rule for a multi-dose vial once a needle has gone in, unless the maker states another date. Medicines mixed from powder carry their own date on the label, in the fridge.
Your vial
Example numbersSince mixing
10daysof 28
Inside the 28 days
18 days to go: the 28-day mark is Mon, Nov 9, 2026.
Kept in the fridge (2–8 °C, 36–46 °F), where the labels of medicines mixed from powder ask for theirs once mixed.
“Once a multi-dose vial is opened (e.g., needle-punctured) the vial should be dated and discarded within 28 days unless the manufacturer states another date for that opened vial.”
Where the 28 days comes from
The CDC’s injection-safety guidance, after the USP’s chapter on sterile compounding, sets one limit for any multi-dose vial once a needle has gone through its stopper: 28 days, unless the maker states another date. It’s a limit for the opened vial, set for infection control, not a measure of any one peptide’s stability.
Example: a vial mixed 10 days ago is on day 10 of the 28, with 18 days to go to the 28-day mark.
Bacteriostatic water, the usual diluent, is itself a multiple-dose vial with benzyl alcohol as its preservative. Its label gives no in-use limit of its own, and on a drug mixed in it, it defers to the drug’s maker:
“Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute.”
What the labels of mixed medicines say
A medicine sold as a powder to mix carries its own date on its label, and the dates differ widely. Both of these ask for the fridge once mixed:
“After reconstitution of the lyophilized powder, the contents of the OMNITROPE vial must be used within 21 days. After the first injection, store the vial in the original carton in a refrigerator at 2° to 8°C (36° to 46°F)”
“If reconstituted solution in vial is not used immediately, then store refrigerated [2°C to 8°C (36°F to 46°F)] until use and discard after 60 days.”
A research peptide mixed at home has no such label, and no agency gives a general shelf life for one. Where its maker gives no date, the 28 days for an opened vial is the general limit a source sets.
Questions
Does keeping it in the fridge stretch the 28 days?
The CDC sets 28 days for any opened multi-dose vial and names no longer limit for a cold one; only the maker’s own date replaces it. The fridge is where the labels of medicines mixed from powder ask for them to be kept: Omnitrope 5.8 mg for 21 days, Pregnyl for 60 days.
What does the bacteriostatic water label say?
It is a multiple-dose vial of water with benzyl alcohol as its preservative, and on a drug mixed in it the label says: “Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute.” It gives no in-use limit of its own.
Sources
- CDC, Preventing Unsafe Injection PracticesMulti-dose vials: the 28-day limit once a vial is opened, after the USP’s General Chapter 797, unless the maker states another date (page dated Mar 26, 2024).
- Bacteriostatic Water for Injection, USP (Hospira), labelA multiple-dose vial of water with 0.9% or 1.1% benzyl alcohol, stored at 20 to 25 °C; on a drug mixed in it, the line quoted above. The label gives no in-use limit of its own. DailyMed, SPL version 20 (May 22, 2026).
- OMNITROPE (somatropin), prescribing informationSection 16.2, Storage and Handling. DailyMed, SPL version 36 (Jul 10, 2025).
- PREGNYL (chorionic gonadotropin), prescribing informationStorage. DailyMed, SPL version 11 (Dec 2, 2025).
Each source read on Oct 19, 2026.
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