Guide
How to reconstitute peptides
Lyophilised (freeze-dried) peptides have to be dissolved before use. Doing it carefully protects the peptide and makes every later measurement accurate.
What you need
- The peptide vial (lyophilised powder, still sealed).
- Bacteriostatic water — sterile water with 0.9% benzyl alcohol.
- A sterile syringe to draw and add the water (a 1 mL or 3 mL syringe is easiest).
- Alcohol swabs.
- A clean, uncluttered work surface.
Step by step
- Let the vial reach room temperature if it was refrigerated, so condensation does not form inside when opened.
- Swab both rubber stoppers (peptide and water) with alcohol and let them dry.
- Draw the chosen volume of bacteriostatic water. The volume sets the concentration — see the maths below.
- Add the water slowly down the inside wall of the peptide vial. Do not squirt it directly onto the powder; some peptides are fragile and foam.
- Swirl gently or roll the vial between your fingers until clear. Never shake. Most peptides dissolve in under a minute; some take a few minutes.
- Check the solution: it should be clear (GHK-Cu will be blue). Cloudiness or particles can mean degradation or contamination.
- Label the vial with the date and concentration, and refrigerate at 2–8 °C.
The concentration maths
Concentration is simply peptide mass divided by water volume:
concentration (mg/mL) = peptide in vial (mg) ÷ water added (mL)
On a standard U-100 insulin syringe, 100 units = 1 mL, so 1 unit = 0.01 mL. To find the volume for a given amount:
units = (amount wanted in mg ÷ concentration in mg/mL) × 100
Worked examples
| Vial | Water | Concentration | 250 µg = | 1 mg = |
|---|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg/mL | 10 units | 40 units |
| 10 mg | 2 mL | 5 mg/mL | 5 units | 20 units |
| 10 mg | 1 mL | 10 mg/mL | 2.5 units | 10 units |
| 20 mg | 2 mL | 10 mg/mL | 2.5 units | 10 units |
Choose a volume that makes your typical measurement land on a readable syringe mark — very small unit counts (under 5) are hard to measure accurately. Use the peptide calculator to check your numbers.
Common mistakes
- Shaking the vial — can shear and denature peptides.
- Using sterile water instead of bacteriostatic water for a multi-use vial — sterile water has no preservative, so it should be used within a day.
- Forgetting what volume you added — always label.
- Mixing up mg and µg — 1 mg = 1,000 µg (mcg). A tenfold error is easy to make.
- Storing at room temperature after reconstitution.
Reconstitution calculator
Vial presets:
Arithmetic aid for laboratory reconstitution. It does not recommend any amount for any use.
Frequently asked questions
How much bacteriostatic water do I add to a 10 mg peptide vial?
There is no single right answer — it sets the concentration. 2 mL gives 5 mg/mL (1 mg = 20 units on a U-100 syringe); 1 mL gives 10 mg/mL. Pick a volume that makes your measurements easy to read.
Can I use sterile water instead of bacteriostatic water?
Yes for single use, but sterile water has no preservative, so a vial made with it should be used within 24 hours. Bacteriostatic water allows multi-dose use for up to 28 days.
Why should you not shake peptides?
Vigorous shaking can cause foaming and physically damage peptide chains. Gentle swirling or rolling is enough.
How long do reconstituted peptides last?
Most last around 3–4 weeks refrigerated at 2–8 °C when made with bacteriostatic water. Stability varies by peptide.