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Someone mixed a peptide powder called GHK‑Cu with a small amount of bacteriostatic (bac) water and then topped it up with plain sterile water, and asked how long the resulting solution will last. In plain terms: they used two different kinds of water to dissolve the peptide and want to know how long that dissolved peptide stays usable and safe. GHK‑Cu is a short peptide (a tiny protein fragment) that’s often talked about for skin healing, collagen stimulation, and wound repair. It’s sold as a dry powder that needs to be dissolved before use. Bacteriostatic water contains a tiny preservative (usually benzyl alcohol) that helps stop bacteria from growing in the liquid. Sterile water has no preservative — it’s just clean water. People reconstitute peptides to make them easy to apply or inject, and the choice of solvent affects how long the liquid remains free of microbes. What the original post describes is a common, practical question but not a rigorous study. It’s a single-person report: they had only 1 ml of bac water for 100 mg of peptide and added 1 ml of sterile water to reach the volume they wanted. That means the final mix is half preserved water and half unpreserved. There’s no experimental data in the post saying how long that exact mixture was tested and shown safe. In general terms, peptide stability and contamination risk depend on the peptide itself, the final concentration, how it’s stored (temperature, light), and whether there’s any preservative. Mixing in sterile water dilutes the preservative, so you can’t assume the same shelf life as a solution made entirely with bacteriostatic water. Why this matters: if you plan to store a reconstituted peptide for days or weeks, you want to avoid bacterial contamination and chemical breakdown. For someone using GHK‑Cu for skin care or experimental self-use, knowing how long a solution stays stable affects safety and effectiveness. If the preservative is diluted enough to be ineffective, the safer choice is to store the solution in the refrigerator and use it quickly, or to reconstitute with only bacteriostatic water and prepare smaller aliquots so you use them up fast. Caveats and risks are important here. I can’t tell you a precise “shelf life” from that lone post because it lacks controlled testing. Many peptide suppliers recommend storing reconstituted peptides in the fridge and using them within a short window (often days to a few weeks) depending on the peptide and solvent. Benzyl alcohol in bac water helps reduce bacterial growth but isn’t a guarantee, especially if diluted. If you’re injecting anything, contamination can cause infections. If you’re unsure, throw it out and reconstitute fresh using the proper solvent, keep work surfaces clean, use sterile syringes, and follow supplier instructions. Also check local regulations and medical advice — peptides aren’t regulated the same way as prescription drugs in many places. Bottom line: diluting bac water with sterile water reduces the preservative’s strength, so treat the mixed solution as less stable and use it quickly, refrigerate, and prioritize safety over saving a little solvent.
Source: r/Peptides