Peptide Storage and Handling

The diluent. Bacteriostatic water is stored at controlled room temperature, 20 to 25 degrees Celsius (68 to 77 °F). The label gives one instruction and does not distinguish between a sealed vial and a punctured one. The in-use period of 28 days comes from USP <797> rather than from the label, which the shelf life page works through.

What the label says about mixtures. This is the part worth quoting, because it is the manufacturer declining to answer the question this page is about:

Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute.

It also instructs aseptic technique on every entry, mixing thoroughly and using promptly, and inspecting the result for clarity and absence of precipitation or discoloration before use.

Source: Bacteriostatic Water for Injection, USP. Hospira, Inc. FDA-approved package insert, via DailyMed. Read 2026-09-20.

Everything else. Refrigerating a reconstituted vial, keeping it out of light, the specific number of weeks it is said to remain good for: these are practices carried over from how peptides are handled in a laboratory, and they are reasonable. They are not label instructions and they are not backed by stability data on an unapproved compound.

That distinction matters because the confident specificity in this niche is not earned. A figure quoted to the week, for a compound with no approved labelling, is someone's practice repeated until it sounded official.

The general shape of what is understood about the class: lyophilised powder is more stable than solution, which is why these products ship dry; cold is gentler than warm; repeated freeze and thaw cycles are worse than steady storage; and light is avoided as a precaution. None of that is specific enough to give you a date, and this site is not going to invent one.

Label the vial when you mix it. The date you first entered it, what is in it, and the concentration you chose. Nothing on a reconstituted vial records any of those, and all three are needed later: the concentration to draw any other dose, and the date for every judgement about whether it is still good.

The reconstitution steps put that last, which is exactly why it gets skipped.

How should bacteriostatic water be stored?

At controlled room temperature, 20 to 25 degrees Celsius. The label gives that instruction for the sealed vial and the opened vial alike and does not ask for refrigeration.

Does a reconstituted peptide need refrigerating?

The bacteriostatic water label does not answer this and says so: it instructs that reconstituted drug solutions should not be stored at all unless the manufacturer of the drug being dissolved directs otherwise. For a compound with no manufacturer guidance, there is no documented answer, and refrigeration is convention rather than instruction.

How long does a reconstituted peptide last?

There is no authoritative figure for compounds that have no approved labelling. Numbers circulate widely and confidently, and they do not come from stability data on the product in your hand.

Does light affect peptides?

Peptides are generally handled as light-sensitive and stored in their carton for that reason. This is standard practice for the class rather than a figure anyone can cite for a specific compound.