Last updated: September 16, 2026 — Version 1.0
Lyophilized peptides are stable for years when kept cold, dry, and dark. They lose purity when they are warm, damp, or exposed to air and light. This guide sets out the laboratory storage conditions PGB’s testing guarantee assumes and explains what a purity number means at different points in a vial’s life. All products are sold for in vitro laboratory research only.
On arrival
- Move vials to cold storage the day they arrive. Lyophilized peptides tolerate the days in transit; they should not sit at room temperature after that.
- Check the lot number on the label against the lot page linked from How We Test. Keep the label intact; it is required for any testing claim.
- Do not open a vial that is not going to be used. The seal and the dry headspace are what preserve it.
Storing sealed lyophilized vials
- Long term: −20 °C (−4 °F) or colder, in a container that keeps out light and moisture. A sealed bag or box with a desiccant packet inside the freezer is enough.
- Short term: 2 to 8 °C (36 to 46 °F) is acceptable for up to about 30 days, sealed and dark.
- Room temperature is not a storage condition. Days are tolerable; weeks and months are not, and the damage does not reverse.
- Before opening a cold vial, let it reach room temperature in its container so condensation forms on the outside, not on the powder.
Compounds that degrade fastest
Peptides containing methionine oxidize on contact with air, and peptides with several asparagine or glutamine residues deamidate in the presence of moisture. Both reactions are slow when frozen and fast at room temperature. In PGB’s catalog the most sensitive compounds include VIP, Semax, MOTS-c, Sermorelin, and Tesamorelin. Treat these as freezer-only and keep them sealed until use.
After reconstitution
A peptide in solution is far less stable than the dry powder. Keep reconstituted material at 2 to 8 °C, protected from light, and use it promptly. Do not freeze and thaw solutions repeatedly. PGB’s testing guarantee applies to sealed lyophilized vials only.
What a purity number means over time
A purity result is a measurement of one vial on one day. PGB tests every lot before release (Round 1) and again from vials pulled from customer inventory after delivery (Round 2). A Round 2 result is older product, and its purity reflects both the lot as shipped and everything that happened to that vial afterward. Under the storage conditions above, purity loss over twelve months is typically well under one percentage point. At room temperature the sensitive compounds listed above can lose several points within a few months.
PGB guarantees that each lot met specification when it shipped, and pauses sales and notifies purchasers when its own post-delivery testing shows a lot has fallen below specification. The full terms, including the claim window and what a claim needs, are in the Returns, Refunds & Reship Policy.
Reserve samples
PGB retains reserve vials from each lot for verification testing. A reserve vial is used to check a customer result only when it has been held under the storage conditions in this guide since PGB received the lot; otherwise the discrepancy goes to a confirmatory test at an independent laboratory.