Preparation
Reconstitution basics
What reconstitution is, which diluents are used for what, why gentle handling matters, and the vocabulary every guide assumes you already know.
What reconstitution means
Reconstitution is the act of adding a liquid (the diluent) to a lyophilized powder so the powder dissolves and the peptide becomes a solution. That is the entire definition. Everything people find intimidating about it is downstream detail: which diluent, how much, and how to describe the resulting concentration.
One boundary note before the details: Therapept explains the vocabulary and the arithmetic. It does not publish step-by-step self-injection guidance, because the context that makes such guidance safe or unsafe — what the material is, whose hands it is in, and why — is exactly what a website cannot see.
The diluents, in one table
| Diluent | What it is | Typical context |
|---|---|---|
| Bacteriostatic water (0.9% benzyl alcohol) | Sterile water with a preservative that limits bacterial growth after the vial is punctured | Multi-use vials where the liquid is drawn more than once; the standard choice in community and clinical discussion of research vials |
| Sterile water for injection | Sterile, preservative-free water | Single-use situations where the entire vial is used at once, because there is no preservative to protect the liquid after puncture |
| Sterile saline (0.9% sodium chloride) | Sterile salt solution, preservative-free | Used for some parenteral products; can affect peptide solubility or stability for specific sequences |
| Sterile bacteriostatic saline | Saline plus benzyl alcohol preservative | Less common; same multi-use logic as bacteriostatic water |
| Acetic acid solutions (very dilute) | Water with a trace of acid | Some peptides — certain GLP-1 analogues and others — are formulated acidic because they dissolve or stabilize better; the manufacturer's documentation states this where it applies |
Why the choice matters
Two different problems live behind the diluent question. The first is contamination: once a vial of sterile water is punctured, it has no defence against bacteria, which is why preservative-containing diluents exist for multi-use vials. The second is the peptide's own chemistry: sequences differ in how happily they dissolve at neutral pH, in saline, or in dilute acid. A manufacturer that specifies a diluent is telling you something measured about their product, not offering a preference.
This is also why Therapept does not answer “which diluent should I use for X?” in the abstract: the honest answer depends on the product's formulation, which lives on the supplier's own documentation.
The dissolution step, conceptually
Lyophilized peptides dissolve — but gently. The standard advice across clinical references and supplier documentation is to let the diluent run down the inside wall of the vial rather than blasting it directly onto the cake, then let the vial sit, swirling occasionally. Peptides are fragile molecules; foaming, violent shaking and aggressive vortexing can shear or denature some sequences, and visible foam is usually peptide-and-air you are not recovering.
Dissolution time varies with the sequence and the concentration. Some vials clear in seconds; others need a few minutes. Undissolved material after standing is information — either the concentration is above the peptide's solubility at that temperature and pH, or something about the solution (wrong diluent, cold temperature) is slowing it down.
After dissolution
Once a peptide is in solution, the stability clock runs much faster than it did for the powder. Storage of the liquid — and how long manufacturers and literature say solutions last — is covered in the storage guide. The arithmetic connecting vial quantity, diluent volume and concentration is covered in concentration math, with a calculator that shows every equation it uses.
Sources
Updated 17 September 2026 · Therapept Editorial · How these guides are built