Storing peptides: keeping them stable before and after mixing

Peptides are delicate molecules, and poor storage is one of the most common reasons a product loses potency. This guide covers general storage principles for both the freeze-dried powder and the mixed solution. Always follow the specific product's guidance and check each peptide's storage note in the library.

Before mixing: the lyophilised powder

In its freeze-dried (lyophilised) form, most peptides are relatively stable and are usually kept refrigerated. Some tolerate freezing for longer-term storage, while others do not — repeated freeze–thaw cycles can damage them. Keep vials dry, sealed and away from light and heat.

After mixing: the reconstituted solution

• Once mixed with bacteriostatic water, peptides are generally kept refrigerated (about 2–8 °C).
• Reconstituted solutions have a limited in-use window — often a few weeks — because peptides degrade in solution over time.
• The benzyl alcohol in bacteriostatic water inhibits bacterial growth, which is why it is preferred for a vial drawn from repeatedly.

What degrades peptides

• Heat and repeated temperature swings.
• Light exposure for light-sensitive peptides.
• Vigorous shaking or foaming, which can denature them — gentle swirling is preferred.
• Time in solution, even when refrigerated.

General education only, not medical advice. Product handling varies — verify with the manufacturer and a licensed clinician.