How to reconstitute peptides
Peptides ship as a dry, freeze-dried powder. Reconstituting means adding a measured amount of bacteriostatic water so you can draw accurate doses. It takes five minutes once you know the steps.
What you need
- The peptide vial, still sealed.
- Bacteriostatic water: sterile water with 0.9% benzyl alcohol, a preservative that keeps a multi-use vial clean.
- Alcohol swabs for both rubber tops.
- A syringe for the water. An insulin syringe holds 1 mL; a 3 mL syringe makes adding 2–3 mL easier.
Watch it done
How much water to add
The amount of water doesn't change how much peptide is in the vial. It changes how concentrated the mix is, and so how many units each dose takes up on the syringe.
Pick a water amount that puts your dose on an easy line, ideally 10 units or more. Smaller numbers are harder to measure accurately.
| Vial | Water | Strength | 250 µg dose | 500 µg dose |
|---|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg/mL | 10 units | 20 units |
| 5 mg | 1 mL | 5 mg/mL | 5 units | 10 units |
| 10 mg | 2 mL | 5 mg/mL | 5 units | 10 units |
| 10 mg | 3 mL | 3.33 mg/mL | 7.5 units | 15 units |
Not sure? The calculator works it out for any vial and dose.
Step by step
Let the vial warm up
- Take it out of the fridge 10–15 minutes early. Cold glass can make the powder clump.
Wash and swab
- Wash your hands. Flip off both plastic caps and wipe each rubber top with a fresh alcohol swab. Let them air-dry.
Draw the water
- Pull the plunger back to your water amount, push that air into the water vial, turn it upside down and draw the water out.
Add it slowly, down the glass
- Push the needle through the peptide vial's top at an angle so the water runs down the inside wall. Don't spray it straight onto the powder.
Swirl, don't shake
- Roll the vial gently between your fingers until it's completely clear. This can take a minute or two. Shaking can damage the peptide.
Check it
- It should look like water. If it's cloudy, has floating bits, or foam that won't settle, throw it out.
Label and refrigerate
- Write the date and strength on the vial (for example "2.5 mg/mL, Oct 5"). Keep it at 2–8 °C and use it within about 4 weeks.
Common mistakes
- Using tap, bottled or plain sterile water. Plain sterile water has no preservative, so a vial you open again and again can grow bacteria.
- Shaking the vial. Swirl gently instead.
- Forgetting what strength you made. Always write it on the vial.
- Mixing up µg and mg. They're 1,000× apart. Read mcg vs mg.
Common questions
Can I use sterile water instead of bacteriostatic water?
Only if you'll use the whole vial in one go. Sterile water has no preservative, so it isn't safe for a vial you'll open repeatedly over days or weeks.
How long does a reconstituted peptide last?
Most guidance says about 3–4 weeks in the fridge at 2–8 °C. Some peptides break down faster, so check the guide for yours.
Does it matter how much water I add?
Not to the total amount of peptide. It only changes how many units each dose is. Choose an amount that makes your dose easy to measure.