Short answer: Keep sealed powder cold, dry and dark, and in the freezer for long-term storage. Once mixed, keep the vial in the fridge at 2 to 8 °C (36 to 46 °F), out of light, not frozen, and date it. Heat, light and moisture all break peptides down without any visible sign, so throw out anything cloudy, discolored or stored warm.
Why storage matters
Peptides lose strength gradually. A vial does not look different at 70% strength, so you can end up taking less than you think. Heat, water, light and air are the main causes.
For approved medicines, follow the label: it gives exact temperatures and time limits. For research peptides there is usually no such data, so the rules below are cautious general practice.
Sealed powder (lyophilized)
Freeze-dried powder is the most stable form because most of the water is gone. Lab suppliers such as Thermo Fisher and Sigma-Aldrich advise:
- Store sealed powder in the freezer (-20 °C) for the long term. A fridge is fine for shorter periods.
- Keep it dry. Let a cold vial warm to room temperature before opening so moisture does not condense inside.
- Keep it dark (in its box or a drawer).
- Avoid freezing and thawing again and again.
A healthy cake is white or off-white and intact. A collapsed, melted-looking or discolored cake, or moisture in a sealed vial, are warning signs.
Mixed vials (reconstituted)
- Fridge at 2 to 8 °C (36 to 46 °F), middle shelf toward the back. Not the door, where temperature swings, and not against the cooling element, where it can freeze.
- Do not freeze a vial you are drawing from. (Labs freeze solutions in single-use portions; that is different from a multi-dose vial you open repeatedly.)
- Date it the day you mix it. Clinics discard multi-dose vials 28 days after first puncture unless the maker says otherwise; that limit is about germs. Lab suppliers advise using dissolved peptides within about a week, so strength may fade sooner.
- Bacteriostatic water slows bacteria. It does not stop the peptide from breaking down.
Light, air and moisture
Peptides that contain cysteine, methionine or tryptophan are more prone to damage by air (oxidation), and peptides in solution break down faster than powder. Keep vials in their box, away from bright light, and away from bathroom steam, kettles and dishwashers. A few silica gel packets in your storage box help keep powder dry.
Warm-ups and power outages
- A few minutes out of the fridge to draw a dose is normal.
- A vial left in a hot car or in the sun should be treated as damaged.
- In a power cut, a closed fridge stays cold for about 4 hours, and a full closed freezer for about 48 hours (24 if half full), per FoodSafety.gov. Keep the doors shut.
Label every vial
Write the compound name, lot number, date mixed, and the discard date. Vials look alike, and memory is not a storage system. Dose Track can keep each vial's mix date and strength; see vials and inventory.
Signs a vial has gone bad
- Cloudiness, haze, flakes or strings in a liquid that should be clear.
- Pink, brown, yellow or other color change.
- An odd smell.
- A collapsed or discolored powder cake, or moisture in a sealed vial.
If it looks wrong, do not use it.
Key points
- Sealed powder: cold, dry, dark; freezer for long-term storage.
- Mixed vials: fridge at 2 to 8 °C, away from the door and the cooling element, not frozen.
- Date every vial; clinics discard multi-dose vials 28 days after first use unless the maker says otherwise.
- Cloudiness, particles, color change or warm storage mean throw it out.
See also: Storage pages by compound · Vials and inventory in Dose Track
This guide is general education, not medical advice. Follow your medicine's label and your prescriber.