Peptide Storage Guide: Refrigerator vs Freezer, Shelf Life After Reconstitution

Proper peptide storage is as important as proper reconstitution. A peptide stored incorrectly before use may have lost significant potency before you inject the first dose. Here's the complete guide.

Two States: Lyophilized vs Reconstituted

Lyophilized (Freeze-Dried) Peptides

This is the powder form peptides arrive in. Lyophilized peptides are remarkably stable:

• Room temperature: Stable for several weeks (for transit). Avoid this long-term.
• Refrigerator (2–8°C): Stable for months. Good for peptides you'll use soon.
• Freezer (-20°C): Most peptides stable for 12–24 months. The gold standard for long-term storage.
• Ultra-cold (-80°C): Essentially indefinite stability for research-grade storage.

Reconstituted (Mixed with BAC Water)

Once you add bacteriostatic water, the clock starts. Peptides in solution are less stable than lyophilized powder:

• Refrigerator (2–8°C): 28–30 days for most peptides — the standard storage period
• Freezer (after reconstitution): Do NOT freeze. Freeze-thaw cycles damage peptide bonds and reduce efficacy. Reconstituted peptides should never be frozen.

Peptide-Specific Shelf Life (Reconstituted)

• BPC-157: 30 days refrigerated
• TB-500: 30 days refrigerated
• Semaglutide: 28 days (matches the Wegovy pen)
• Tirzepatide: 28 days
• CJC-1295 (no DAC): 30 days
• Ipamorelin: 30 days
• IGF-1 LR3: 21 days — less stable than most peptides
• Epithalon: 10 days only — very short shelf life. Plan your dosing accordingly or prepare smaller batches.
• GHK-Cu: 30 days
• PT-141: 30 days

Why Refrigerator, Not Freezer, After Mixing

Peptides in solution expand slightly when frozen. The freeze-thaw cycle causes:

• Ice crystal formation that can disrupt peptide secondary structure
• pH changes that can destabilize the compound
• Aggregation — peptides clumping together, reducing individual molecule availability

None of these effects are visible — the solution looks identical. But potency can be reduced 10–50% after multiple freeze-thaw cycles.

The Epithalon Exception

Epithalon is a tetrapeptide with an unusually short post-reconstitution shelf life of ~10 days. If you're running a 20-day Epithalon course, reconstitute a second vial partway through rather than mixing the whole course at once. Store unmixed vials in the freezer at -20°C until needed.

Light and Temperature Exposure

Most peptides are light-sensitive to varying degrees. Keep vials away from direct sunlight and fluorescent lights — amber vials help, but all vials should be stored opaque or in a box. Don't leave vials on a windowsill or in a bright area even briefly.

Brief temperature excursions during preparation (drawing a dose, mixing) are fine. What matters is the storage temperature, not momentary room temperature exposure.

Labeling: The Step Most People Skip

Always label every vial immediately after reconstitution with:

• Peptide name
• Concentration (e.g., "2,500 mcg/mL")
• Date reconstituted
• Discard date (reconstitution date + shelf life)

This seems obsessive until you have 4 vials in your fridge and can't remember which one you mixed last week.

When to Discard

Discard reconstituted peptide if:

• Past the discard date
• Solution becomes cloudy or develops particles
• Color changes significantly
• Any sign of contamination

A contaminated or degraded peptide is at best ineffective and at worst potentially harmful. When in doubt, discard.

→ Use our Peptide Storage & Expiry Calculator to track doses remaining and expiry dates for all your vials.