The short answer
Lyophilized (powder) peptides are stable at room temperature during shipping but should be kept refrigerated (2–8 °C) for storage beyond a few weeks, or frozen (−20 °C) for long-term holding. Reconstituted peptides must be refrigerated and used within ~28 days. Never repeatedly freeze and thaw a reconstituted vial — each cycle degrades the peptide bonds and reduces potency.
−20 °C (frozen)
Shelf life: 24+ months
Long-term storage. Stable short-term at room temp.
2–8 °C (fridge)
Shelf life: 12–24 months
Standard storage for active inventory.
2–8 °C (fridge)
Shelf life: ~28 days
Never freeze. Protect from light. Use promptly.
Storing lyophilized (powder) peptides
Lyophilized peptides are shipped as a dry cake or powder and are the most stable form. They tolerate ambient temperatures for the days or weeks involved in transit, which is why most suppliers ship them without cold packs. However, heat, light, and moisture all accelerate degradation, so for storage longer than a few weeks, move the vial to a refrigerator at 2–8 °C. For holding inventory across many months, a −20 °C freezer maximizes shelf life — 24 months or longer for most sequences.
Keep vials upright and away from the freezer door, where temperature fluctuates most. Before reconstituting, inspect the cake: a uniform white disc is normal; discoloration, collapse, or clumping can signal moisture ingress and reduced potency. Always let a frozen vial reach room temperature before opening it to avoid condensing atmospheric moisture onto the powder.
Storing reconstituted peptides
Once a peptide is dissolved — typically in bacteriostatic water for injection — its shelf life drops sharply. The dissolved peptide is far more vulnerable to hydrolysis, oxidation, and microbial growth. The general rule is refrigerate at 2–8 °C and use within about 28 days. Bacteriostatic water contains a benzyl-alcohol preservative that extends usable life versus plain sterile water, but 28 days remains the standard reference window.
Protect reconstituted vials from light (amber vials or a closed fridge bin) and never subject them to repeated freeze/thaw cycles. Freezing a reconstituted solution forms ice crystals that physically disrupt peptide bonds; the damage compounds with each cycle. If a long study requires many doses, pre-aliquot into single-use volumes and freeze each aliquot once — never refreeze after thawing.
Per-compound storage notes
Retatrutide
Lyophilized vials keep 12–24 months refrigerated. After reconstitution with bacteriostatic water, refrigerate and use within ~28 days. Do not freeze a reconstituted vial. Retatrutide's long half-life (~6 days) means a single reconstituted vial typically covers a full multi-week course.
Semaglutide
Stable as a powder refrigerated for 12–24 months. Reconstitute to a workable concentration (commonly 2–4 mg/mL) and use within ~28 days refrigerated. Discard if the solution becomes cloudy or discolored.
BPC-157
Lyophilized BPC-157 is stable refrigerated long-term. Reconstituted, keep refrigerated and use within 3–4 weeks. Short room-temperature excursions during dosing are acceptable; prolonged heat or freeze/thaw is not.
GHK-Cu (Copper peptide)
Powder is stable refrigerated. Once reconstituted, copper peptides are more oxidation-sensitive than most — minimize headspace, keep cold, and use promptly. A slight blue tint is normal; brownish discoloration signals oxidation.
Signs a vial has degraded
- • Discoloration of the powder or solution (brown, yellow, or cloudy).
- • A collapsed, melted, or clumped lyophilized cake.
- • Visible particles or precipitate after reconstitution.
- • Loss of the expected research effect at a previously effective dose.
- • A vial that has exceeded its labeled retest or use-by date.