Peptide stability and storage — degradation kinetics

This is a much-needed resource. Let me add the practical storage recommendations organized by peptide form:

Lyophilized (freeze-dried) powder — MOST STABLE FORM:

• Room temperature: stable for 1-2 years (in sealed vial, desiccated)
• Refrigerated (2-8°C): stable for 2-4+ years
• Frozen (-20°C): stable for 5+ years
• Key: keep the vial sealed with the cap/septum intact. Moisture is the enemy of lyophilized peptides. The vacuum or nitrogen atmosphere in the sealed vial is protective.

Reconstituted solution (peptide + BAC water):

• Room temperature: 1-3 days (unacceptable for regular use)
• Refrigerated (2-8°C): 3-6 weeks depending on the peptide
• Frozen (-20°C): 3-6 months (but see below on freeze-thaw)
• The bacteriostatic water (0.9% benzyl alcohol) prevents microbial contamination but does nothing to prevent chemical degradation of the peptide itself.

Critical rule: DO NOT repeatedly freeze and thaw reconstituted peptides. Each freeze-thaw cycle can cause aggregation and loss of potency. If you freeze reconstituted peptide, aliquot it into single-use portions first.

This is great info. Quick question — I ordered a batch of BPC-157 vials (6 x 5 mg) and I won't use all of them for months. Should I keep the unopened lyophilized vials in the fridge or freezer?

Fridge is perfectly fine for a few months. If you're storing for 6+ months, freezer is slightly better but honestly the difference at those timeframes for lyophilized peptides is minimal. The key thing is:

• Keep them sealed (don't puncture the septum until you're ready to reconstitute)
• Keep them away from light (store in a box or drawer in the fridge, not on a glass shelf)
• Keep them dry (if you're worried about humidity in your fridge, put them in a sealed container with a desiccant packet)

Lyophilized peptides are remarkably stable. I've used BPC-157 vials that sat in my fridge for 8 months with no noticeable loss of efficacy. The peptide industry ships these at room temperature for a reason — they can handle a few days of transit without degradation.

What about specific peptide stability differences? Not all peptides are created equal in terms of fragility.

From my experience and reading:

• Most stable: BPC-157, TB-500, Ipamorelin — these are relatively robust peptides without highly labile residues. Reconstituted, they hold up well for 4-6 weeks refrigerated.
• Moderately stable: CJC-1295 (with or without DAC), Selank, Semax — good for 3-4 weeks reconstituted and refrigerated.
• Less stable: GnRH analogs, some growth factor peptides, and anything with multiple cysteine residues (disulfide bonds can scramble). Use within 2-3 weeks of reconstitution.
• Semaglutide/tirzepatide: The pharmaceutical formulations are specifically designed for stability with excipients and pH buffers. The multi-dose pens are rated for 56 days (8 weeks) at room temperature once in use. These are among the most stable peptide products available because billions of pharma R&D dollars went into the formulation.