Reconstituting a peptide means dissolving the lyophilised powder in a liquid. The standard choice is bacteriostatic water with 0.9% benzyl alcohol. The liquid is added slowly down the wall of the vial, the vial is never shaken, and the finished solution is kept in the fridge for up to about four weeks.
This article describes the technical side of preparing a solution: which water to choose, how to combine it with the powder and how to store the result. It is not a set of instructions for use in humans. Peptides in our shop have the status of research material, the checkout is in English and prices are shown in Polish zloty.
What is peptide reconstitution?
Reconstitution means combining a lyophilised peptide with a solvent so that a solution of known concentration is produced. A peptide is sold in dry form because it is stable in that state and resistant to breakdown. Once liquid is added it becomes unstable, and from that moment it needs refrigeration.
Which water should you use: bacteriostatic, for injection or sterile?
Bacteriostatic water is chosen most often, because it contains an agent that inhibits bacterial growth and allows the finished solution to be kept longer.
| Type of water | What it contains | How long the solution keeps in the fridge |
|---|---|---|
| Bacteriostatic water | 0.9% benzyl alcohol as a preservative | about 4 weeks |
| Water for injection (sterile) | sterile, no bacteriostatic agent | much shorter, use quickly |
| Distilled water | free of minerals, neither sterile nor bacteriostatic | not suitable |
Choosing bacteriostatic water is mainly a question of how long the solution lasts, not of whether the peptide dissolves. The peptide will dissolve in any of these, but only with a preservative will the solution last several weeks. The three types are compared in the article on bacteriostatic water and water for injection.
How do you reconstitute a peptide?
- Take out the vial of peptide and the vial of water and wait until both reach room temperature.
- Wipe the rubber stoppers of both vials with an alcohol swab, in a circular motion for 5 to 10 seconds, and wait for the alcohol to dry.
- Draw into the syringe the volume of water given in the instructions for that particular peptide.
- Insert the needle into the peptide vial and deliver the water slowly, roughly 1 ml every 10 to 15 seconds, aiming the stream at the wall of the vial rather than at the powder.
- Set the vial aside and let the powder dissolve by itself. If needed, roll the vial gently between your fingers for 30 to 60 seconds.
- Never shake the vial. Shaking creates foam and damages peptide molecules.
The finished solution should be clear. A cloudy liquid or visible particles mean something went wrong, and such a solution is not used.
How do you store the finished solution?
Keep the solution in the fridge, at 2 to 8 degrees Celsius. With bacteriostatic water it lasts about four weeks. Do not freeze it, because ice crystals destroy the structure of the peptide during thawing. Storage conditions and times for both the dry powder and the finished solution are covered in the article on storing peptides.
What are the most common mistakes when dissolving peptides?
- Shaking the vial instead of rolling it gently.
- Pouring water straight onto the powder instead of down the wall.
- Using water straight from the fridge, which slows dissolution.
- Keeping the finished solution outside the fridge or in the freezer.
- Skipping disinfection of the stopper before puncturing it.
Frequently asked questions
Will a peptide dissolve in ordinary water?
It will dissolve, but a solution without a bacteriostatic agent has to be used much sooner. Bacteriostatic water allows storage in the fridge for about four weeks.
Why must the vial not be shaken?
Shaking introduces air into the solution, creates foam and exposes peptide molecules to damage. Gently rolling the vial is enough to dissolve the powder.
How long can a reconstituted peptide be kept?
With bacteriostatic water, a solution kept in the fridge at 2 to 8 degrees Celsius lasts about four weeks. It should not be frozen.
What should you do if the solution is cloudy?
A cloudy solution, or one with visible particles, is not used. Clarity is the basic sign that reconstitution went correctly.
How much water gives a known concentration?
Concentration is the number of milligrams of peptide divided by the number of millilitres of water. A 10 mg vial with 2 ml of water gives 5 mg per millilitre, and with 5 ml it gives 2 mg per millilitre.
Where this information comes from
The reconstitution procedure, the composition of bacteriostatic water, the method of adding the liquid and the storage rules come from material published by Molequa and PurePoint, checked on 31 August 2026. Both sources give 0.9% benzyl alcohol in bacteriostatic water and about four weeks of storage for the solution in the fridge.