Quick answer
Do peptides need refrigeration?
Reconstituted peptides: yes. Sealed lyophilized (freeze-dried) powder: not strictly short-term, but refrigeration is recommended.
Two states, two rules
Once reconstituted, keep the solution refrigerated (2–8 °C) and use it within about a week, or freeze it in single-use portions. Sealed lyophilized powder is stable short-term at a cool room temperature, but lasts much longer refrigerated, or frozen (−20 °C) for the long term.
Fridge or freezer: what each one is for
- Sealed powder you will use within weeks: the fridge (2–8 °C) is fine. For anything longer, the freezer (−20 °C) is the standard.
- Powder that has just arrived: lyophilised vials are normally shipped at room temperature, which they tolerate for short periods. Put them in the fridge or freezer when the parcel arrives.
- A solution you are using now: the fridge, for up to about a week.
- A solution you want to keep: divide it into single-use portions and freeze them at −20 °C or colder. Manufacturers give a few weeks for frozen solutions.
- Before you open a cold vial: let it reach room temperature first.
Sources: Sigma-Aldrich (Merck) · Bachem
What to avoid
Heat, light and repeated freeze-thaw all degrade peptides. For the full breakdown see storing lyophilized peptides.
Frequently asked questions
Is it ruined if it sat out for a few hours?
A brief time at room temperature is usually fine, but prolonged heat or light degrades peptides. If a reconstituted solution looks cloudy or discoloured, discard it.