How to store peptides

Most peptides ship as a dry, freeze-dried powder (you'll see it called lyophilized). With the water removed, the powder is far more stable than a mixed vial.

Once you add water, the clock starts. The peptide slowly breaks down in liquid, and the vial can pick up bacteria every time a needle goes in.

So the simple rule: leave vials as powder until you're ready to use them.

• Cold, dark and dry. A fridge works for vials you'll use soon. A freezer is better for ones you're keeping longer.
• Keep it in the box or wrap it. Light breaks peptides down.
• Let it warm up before opening. A cold vial opened in a warm room pulls in moisture. Give it a few minutes on the counter first.
• Shipping at room temperature is usually fine for powder over a few days. Heat is the bigger worry than time.

Check each compound's page for its own storage notes. Some are fussier than others.

• In the fridge, 36–46°F (2–8°C). Not the door, where the temperature swings.
• Don't freeze it. Freezing and thawing a mixed peptide can damage it.
• Keep it out of light.
• Don't shake it. Swirl gently. Shaking can damage the peptide.
• Label it with the date you mixed it and how much water you added. You'll need both later.

You'll see 28 days quoted a lot. That number comes from bacteriostatic water: multi-dose vials are generally labeled for use within 28 days of the first needle going in, because the preservative only holds off bacteria for so long.

It's a sensible ceiling, not a guarantee. Some peptides break down faster than that even in the fridge. Each compound page lists its own shelf life after mixing. Go by whichever is shorter.

Mixed with plain sterile water instead of bacteriostatic? There's no preservative, so it's meant to be used right away, not stored.

Toss the vial if:

• The liquid is cloudy, or has specks or strands floating in it
• The color has changed
• It was left out warm for hours, or frozen after mixing
• It's past its date, or you can't remember when you mixed it
• The rubber stopper looks damaged

If you aren't sure, don't use it. A new vial costs less than an infection.

• Carry powder if you can and mix when you arrive.
• For a mixed vial, use an insulated case with a cold pack. Don't let the vial touch ice directly.
• Keep it in your carry-on. Cargo holds get very cold and very hot.