Should peptides be kept in the fridge?
Once reconstituted, yes. As sealed lyophilized (freeze-dried) powder, it is not essential in the short term, though the fridge is still the better place.
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Solution versus powder
A reconstituted solution belongs in the fridge at 2–8 °C. Its usable life depends on the peptide and the diluent; a common conservative rule for an opened multi-dose vial is 28 days. Sealed lyophilized powder holds up for short periods at a cool room temperature. It keeps much longer in the fridge, and for long-term storage it is best frozen at −20 °C.
What damages peptides
Heat, light and repeated rounds of freezing and thawing all break peptides down. Our guide to storing lyophilized peptides covers each of these in detail.
Common questions
A vial sat out for a few hours. Is it still usable?
A short spell at room temperature is usually not a problem. Long exposure to heat or light does degrade peptides. If a reconstituted solution has gone cloudy or changed colour, discard it.