How to Reconstitute Peptides
Reconstituting a peptide means adding bacteriostatic water to the freeze-dried (lyophilized) powder so you can inject a measured dose. If you've just received a vial with a small disc of powder at the bottom, this is where you start.
- Clean the vial stopper with an alcohol swab. Let it dry completely.
- Draw bacteriostatic water into a syringe. We recommend 2 mL for most peptides. Most vials hold 3 mL or less.
- Inject the water slowly into the vial, aiming at the glass wall — not directly onto the powder. This prevents damaging the peptide.
- Gently swirl the vial until the powder is fully dissolved. Do not shake.
- Store in the refrigerator. Most reconstituted peptides last 4–6 weeks refrigerated.
After reconstitution, your vial won't be completely full — that's normal. A typical vial holds about 3 mL, and you're adding 1–3 mL of water. The dose is based on concentration, not how full the vial looks.
How to Draw a Dose
Drawing liquid from a sealed vial requires injecting air first. This equalizes the pressure inside the vial so the liquid flows smoothly into the syringe.
- Clean the vial stopper with a fresh alcohol swab.
- Pull back the plunger to draw air into the syringe — the same volume you plan to withdraw (e.g., if you need 20 units of liquid, draw 20 units of air).
- Insert the needle through the vial stopper and push the plunger to inject the air into the vial.
- Invert the vial so the stopper faces down, with the needle tip submerged in the liquid.
- Pull back the plunger slowly to your target unit mark.
- Check for air bubbles. If you see any, gently flick the barrel to move them toward the needle, then push the plunger slightly to force them back into the vial. Readjust to your target volume.
- Remove the needle from the vial. You're ready to inject.
Understanding Peptide Dosing
The key concept is concentration. When you add 2 mL of water to a 10 mg vial, you get a concentration of 5 mg/mL. To dose 2.5 mg, you need 0.5 mL — which is 50 units on a standard insulin syringe.
Insulin syringes are marked in "units," where 100 units = 1 mL. So the math is simple: multiply the volume in mL by 100 to get your unit mark. The calculator above does this for you automatically.
Frequently Asked Questions
How much bacteriostatic water should I add?
We recommend 2 mL for most peptides. More water means a larger draw volume on your syringe, which makes it easier to measure small doses precisely. Most vials hold 3 mL or less, so don't add more than that.
Why is my vial not full after adding water?
Completely normal. The powder takes up almost no space. A typical vial is a 3 mL container, and you're adding 2 mL of water — so it'll be about two-thirds full. Your dose is determined by the concentration, not the fill level.
Why do I need to inject air into the vial first?
The vial is sealed, so removing liquid creates a vacuum that makes it hard to draw. Injecting an equal volume of air first keeps the pressure balanced, allowing the liquid to flow easily into the syringe.
Can I use regular water instead of bacteriostatic water?
Bacteriostatic water contains 0.9% benzyl alcohol, which prevents bacterial growth and allows you to use the vial over multiple doses. Sterile water is an alternative but should be used within 24 hours. Never use tap water.
How long does a reconstituted peptide last?
When mixed with bacteriostatic water and stored in the refrigerator, most peptides last 4–6 weeks. Keep the vial upright and avoid temperature fluctuations.