GuideHow to reconstitute peptides
Reconstitution just means mixing a freeze-dried peptide powder with liquid so it can be drawn into a syringe. The mechanics are simple, and the only arithmetic that matters is turning your vial size and water amount into a concentration you can dose from.
Reviewed for accuracy · Last reviewed July 7, 2026 What you need
Most people reconstitute with bacteriostatic water, which contains a small amount of benzyl alcohol to limit microbial growth so the mixed vial keeps for weeks in the fridge. Sterile or plain water works for a single use but does not have that preservative.
- The peptide vial (a freeze-dried powder or pellet)
- Bacteriostatic water
- A larger syringe to add the water, plus insulin syringes to dose
- Alcohol swabs and a clean surface
Step by step
Add the water slowly and let the peptide dissolve on its own. Do not shake it, and do not spray the water directly onto the powder.
1Wipe the tops of both vials with an alcohol swab and let them dry.
2Draw your chosen amount of bacteriostatic water into a syringe.
3Insert the needle into the peptide vial and let the water run gently down the inside wall of the vial, not straight onto the powder.
4Leave the vial to sit until the powder fully dissolves. Swirl gently if needed, but never shake.
5Store the reconstituted vial in the refrigerator and label it with the date.
Working out the concentration
Concentration is simply the peptide amount divided by the water you added. A 10 mg vial mixed with 2 mL of water is 5 mg/mL. To find how much to draw for a dose, divide the dose by the concentration to get the volume in mL, then multiply by 100 to get units on a U-100 insulin syringe.
Rather than do this by hand each time, use the calculator, which returns the concentration and the exact draw for any vial size, water amount, and dose.
FAQ
How much bacteriostatic water should I add to a peptide vial?There is no single correct amount. More water makes a weaker, larger-volume solution that is easier to measure at small doses; less water makes a stronger solution that fits more dose in one syringe. Pick an amount, then calculate the concentration from it.
Can I shake the vial to dissolve it faster?It is generally advised not to shake peptide vials. Add the water gently down the vial wall and let the powder dissolve on its own, swirling lightly if needed.
How long does a reconstituted peptide last?It varies by compound, but many reconstituted peptides are kept refrigerated for roughly 2 to 4 weeks. Check the specific compound page for its window.