Peptides are sensitive molecules, and how you store them has a direct effect on whether they remain intact and usable. Store them well and a lyophilised peptide can remain stable for a very long time. Store them badly — warm, in the light, or through repeated freeze-thaw cycles — and they can degrade before you ever use them. This guide covers everything you need to know.
*This is a laboratory research guide. All Peptide Pal compounds are for in-vitro research only.*
## Lyophilised vs reconstituted: two different rules
The single most important thing to understand is that a peptide in powder form and the same peptide dissolved in liquid have very different storage needs.
**Lyophilised (freeze-dried powder):** very stable. In its sealed vial, kept cool and dry, it lasts for months to years.
**Reconstituted (dissolved in liquid):** far less stable. Once in solution, the clock starts — it must be refrigerated and used within weeks.
## Storing lyophilised peptides
For short-term storage (up to a few weeks before use), a standard refrigerator at **2–8°C** is perfectly adequate. Keep the vial sealed and away from light.
For long-term storage (months or more), the **freezer at -20°C or below** is best. At freezer temperatures, a well-sealed lyophilised peptide can remain stable for a year or more.
In both cases, keep the vial away from moisture and light — both accelerate degradation.
## Storing reconstituted peptides
Once you have added bacteriostatic water, the solution must live in the **refrigerator at 2–8°C**. Do not leave it at room temperature.
How long it lasts depends on the compound, but because bacteriostatic water contains a preservative (benzyl alcohol), a properly refrigerated solution typically remains usable for several weeks. Always defer to the specific guidance in your product documentation.
**Avoid freezing reconstituted solutions** unless the documentation explicitly permits it. Freezing and thawing forms ice crystals that mechanically damage peptide chains.
## The enemy: freeze-thaw cycles
If you do store peptides frozen, the biggest risk is repeatedly freezing and thawing the same vial. Each cycle stresses and degrades the molecule.
The solution used in professional labs is **aliquoting** — dividing a reconstituted peptide into several small portions before freezing (if freezing is appropriate for that compound), so you only thaw what you need and never refreeze the rest.
## A quick reference
- **Lyophilised, short term:** fridge, 2–8°C, sealed, dark
- **Lyophilised, long term:** freezer, -20°C or below
- **Reconstituted:** fridge, 2–8°C, use within weeks, do not freeze
- **Always:** away from light and moisture; avoid repeated freeze-thaw
## Handling mistakes that quietly ruin peptides
- Leaving vials on the bench at room temperature between uses
- Storing near a fridge door (temperature swings every time it opens)
- Exposing vials to direct light
- Refreezing a previously thawed solution
- Reconstituting with non-preserved water and then trying to store it
## Summary
The rule of thumb is simple: **powder is tough, solution is fragile.** Keep lyophilised peptides cold, sealed and dark; keep reconstituted peptides refrigerated and use them within weeks; and never put a delicate compound through repeated freeze-thaw cycles.
Every peptide we supply arrives with documentation and a Certificate of Analysis. Browse the [full range](/pages/buy-peptides), see the [research behind each compound](/pages/studies), or [ask our team](/pages/support) about storing a specific peptide.
---
*All compounds supplied by Peptide Pal are strictly for in-vitro laboratory research and are not for human consumption, self-administration, or medical use.*