If you've ever found a vial in the back of a -20°C freezer from three years ago and wondered whether it was still good, this article is for you.

Lyophilised peptide: stable for years when stored right

Lyophilisation (freeze-drying) removes water from the peptide while preserving its structure. In the dry state, the main degradation pathways — hydrolysis, oxidation, deamidation — all slow dramatically because they require water as a reactant. A properly lyophilised peptide stored at -20°C in a sealed vial is stable for 24 months from the date of manufacture, with less than 1% degradation observed in accelerated stability studies.

The key word is properly. Lyophilised peptide is hygroscopic — it absorbs water from the air. Once you've opened the vial, the clock starts ticking faster. A vial that has been opened, left at room temperature for 30 minutes, then re-closed and stored at -20°C will have absorbed enough moisture to lose several months of effective shelf life.

Best practice: Open the vial in a dry environment (glove box, dry cabinet, or low-humidity room), allow the contents to equilibrate to room temperature before opening (otherwise condensation forms inside the vial as it warms), reconstitute immediately, and never return unused reconstituted peptide to the original vial.

Reconstituted peptide: 30 days, refrigerated

Once you add bacteriostatic water (0.9% benzyl alcohol) or another reconstitution solvent, the peptide becomes a dilute aqueous solution and degradation accelerates. The standard recommendation for most research peptides is:

• 2–8°C (refrigerator, not freezer)
• Bacteriostatic water (BAC 0.9%) as solvent
• Use within 30 days
• Avoid freeze-thaw cycles

Bacteriostatic water contains 0.9% benzyl alcohol which inhibits bacterial growth in the solution. Sterile water for injection (no preservative) is not appropriate for multi-use vials — it will support bacterial growth within days.

If you need to store reconstituted peptide for longer than 30 days, aliquot into single-use vials and freeze at -20°C. Each aliquot is then single-thaw, single-use. Most peptides tolerate one freeze-thaw cycle without significant degradation; some (particularly Cys-containing peptides) tolerate two. Beyond that, expect measurable loss of activity.

Cold-chain shipping: what it actually protects against

We ship every order in an insulated mailer with a phase-change cold pack, regardless of destination or season. This is more than most competitors do, but it's worth being honest about what it accomplishes:

• What it does protect against: Brief exposure to elevated temperatures (above 30°C) that can degrade peptide during the first 48-72 hours of international transit. Particularly relevant for shipments transiting tropical airports in summer.
• What it doesn't protect against: Long-term improper storage after delivery. If you receive a peptide and leave it on your bench at 25°C for a week, no amount of cold-chain shipping can save it.

Lyophilised peptide is stable at room temperature for at least 14 days without measurable degradation (verified by our own stability studies on Tirzepatide, Semaglutide, BPC-157, GHK-Cu). The cold pack is a margin of safety for the transit window, not a requirement for routine handling.

If your shipment is delayed in customs and the cold pack arrives warm or fully thawed, the peptide is almost certainly still fine — particularly for lyophilised material. We test stability at 40°C for 7 days as part of our release protocol; the limit is no observable degradation.

Specific molecule considerations

Most peptides follow the standard rules above, but a few have known quirks:

• Selank, Semax: Both contain a Pro-Gly-Pro motif that can undergo slow diketopiperazine (DKP) formation in acidic conditions. We lyophilise these at pH 7-8 specifically to suppress this. Do not acidify these peptides.
• CJC-1295 with DAC: The DAC modification includes a maleimide linker that is reactive toward thiols. Do not store in the presence of reducing agents (DTT, β-mercaptoethanol).
• NAD+: Highly hygroscopic and sensitive to hydrolysis. Store desiccated. Use molecular-biology-grade water (not Tris buffer) for reconstitution.
• MOTS-c: Mitochondrial-derived peptide; can form disulfide-linked dimers if not handled anaerobically. We ship reduced (monomer) form; the dimer is the degradation product.

When to throw it out

If the lyophilised powder looks discoloured (yellow or brown for a peptide that should be white), if it doesn't fully dissolve in BAC water, if the solution is hazy or contains visible particles, or if your bioassay shows unexpected loss of activity — discard the vial. We will replace it under our CoA-mismatch refund policy if the published CoA also shows those characteristics, but most degradation comes from handling after the vial leaves our facility.

The exception is BPC-157 and a few other peptides that can have a faint off-white appearance — that's normal. The standard is that any visible colour change (yellow/brown) is a degradation flag.

---

Helix peptide research and stability team. Last reviewed July 2026.