Peptide Storage 101: Temperature, Light & Shelf Life
Improper storage is one of the most common — and most avoidable — causes of inconsistent results in peptide research. The good news is that the rules are simple once you understand the two states a peptide moves through: lyophilized powder, and reconstituted solution.
Two States, Two Sets of Rules
Every peptide you receive starts as a lyophilized (freeze-dried) powder — a stable, dry cake sealed in a vial. Storage requirements at this stage are forgiving. Once you add Bacteriostatic Water, the peptide becomes a reconstituted solution, and the rules change: the clock starts on shelf life, and temperature and light exposure begin to matter immediately.
Most storage mistakes happen because researchers apply lyophilized-powder rules (or no rules) to a reconstituted vial. The two states should be thought of as entirely separate storage problems.
Storing Lyophilized Powder
Most lyophilized peptide powders are stable at room temperature for weeks and indefinitely when refrigerated. The dry, sealed state protects the peptide from the hydrolysis and microbial growth that become concerns once water is introduced.
- General rule: a cool, dry, dark place (a drawer or cabinet away from direct sunlight and heat sources) is sufficient for most compounds before reconstitution.
- Exception — NAD+: should be refrigerated even in powder form, as it is comparatively less stable than other lyophilized peptides.
- Light-sensitive powders: NAD+ and MT-2 (Melanotan 2) should be kept away from direct light even before reconstitution.
After Reconstitution: The 2-8°C Rule
Once Bacteriostatic Water is added, refrigerate the vial at 2-8°C immediately. This is the single most important storage rule for reconstituted peptides. At refrigerator temperature, most peptides reconstituted in BAC Water remain stable for 28-42 days.
A small number of compounds have a shorter window: NAD+ and Glutathione are stable for 14-21 days after reconstitution, even when refrigerated correctly. Always write the reconstitution date on the vial label — it's the easiest way to track which window applies and avoid using a vial past its stability period.
Why Not to Freeze Reconstituted Peptides
It's tempting to assume that colder is always better — but freezing a reconstituted peptide solution is not recommended. As the solution freezes, ice crystals form and grow within the liquid. This process can physically disrupt the peptide chain (a phenomenon sometimes called freeze-thaw damage) and can also concentrate or unevenly distribute the peptide within the vial as water separates into ice, altering the effective concentration when thawed.
Light-Sensitive Compounds
Some peptides degrade measurably faster when exposed to light, especially after reconstitution. NAD+, MT-2 (Melanotan 2), and Glutathione fall into this category and should be wrapped in aluminum foil or kept in an opaque container as soon as they're reconstituted.
This is a simple, low-cost step — a few wraps of foil around the vial — but it meaningfully extends how long these compounds retain full potency within their stability window.
Quick Reference Table
| Compound | Powder Storage | Reconstituted Stability | Light-Sensitive? |
|---|---|---|---|
| Most peptides (BPC-157, CJC-1295, GHK-Cu, MOTS-C, Tesamorelin, GLP3-R, etc.) | Cool, dry, dark — room temp OK | 28-42 days @ 2-8°C | No |
| NAD+ | Refrigerate even as powder | 14-21 days @ 2-8°C | Yes — wrap in foil |
| Glutathione | Cool, dry, dark | 14-21 days @ 2-8°C | Yes — wrap in foil |
| MT-2 (Melanotan 2) | Keep away from light | 28-42 days @ 2-8°C | Yes — wrap in foil |
For exact reconstitution volumes and concentrations for every compound we carry, see the full Reconstitution Guide.
Signs of Degradation
- Cloudiness or particulate matter in a solution that was previously clear can indicate the peptide has begun to break down or precipitate out of solution.
- Color change beyond a compound's normal characteristic appearance (e.g., GHK-Cu's blue tint is normal — a dramatic shift in that color is not).
- Past the stability window — even if a solution looks normal, a vial reconstituted more than 28-42 days ago (or 14-21 days for NAD+/Glutathione) should be treated with caution.
If any of these signs are present, it's good practice to discard the vial and reconstitute a fresh one rather than rely on results from a degraded sample.