Short answers to the questions researchers most often ask about storing, mixing and handling GHK-Cu, the copper(II) complex of the tripeptide Gly-His-Lys. Each answer links to the longer section of this reference where the chemistry is explained.
Why is GHK-Cu blue?
The blue comes from the copper(II) ion bound to the peptide, not from a dye. The complex absorbs light in a band at 580 to 600 nm, which leaves the powder and its solutions blue (Mateescu et al., Pharmaceutics, 2026). A clear blue solution is normal, deeper at higher concentration and paler when more water is used. More in why GHK-Cu is blue.
What should GHK-Cu be mixed with?
Bacteriostatic water, which is sterile water with 0.9% benzyl alcohol. It dissolves GHK-Cu readily and contains none of the phosphate, citrate, chelators or proteins that compete with the peptide for its copper (Mateescu et al., Pharmaceutics, 2026). Volumes and concentrations for 50 mg and 100 mg vials are on the GHK-Cu reconstitution page.
Can GHK-Cu be dissolved in acetic acid or saline?
It does not need acetic acid, and acid is best avoided: a lower pH lets protons compete for the nitrogen atoms that hold the copper (Lau and Sarkar, Biochem J, 1981). Plain saline does not break the complex, but it offers no benefit over bacteriostatic water, and phosphate-buffered saline introduces a copper competitor. See GHK-Cu solubility.
How long does GHK-Cu last after mixing?
Mixed with bacteriostatic water and kept at 2 to 8 °C in the dark, it lasts 8 to 12 weeks under our handling guidance, with quality slowly fading from around week 6 to 8. Full windows are on How long does GHK-Cu last?.
How should unmixed GHK-Cu powder be stored?
Sealed and dry, in its box: at 2 to 8 °C for the weeks a vial is in use, or at minus 20 °C for months. Let a cold vial reach room temperature before opening it so moisture does not condense on the powder.
Can you freeze GHK-Cu?
Sealed lyophilised powder, yes. A mixed vial that will be opened again should not be frozen and thawed, because repeated cycles damage peptides in solution. Laboratories that need frozen stock freeze single-use aliquots once.
Is GHK-Cu sensitive to light?
Yes, more than most peptides. Both the copper centre and the histidine imidazole ring are flagged as targets for light damage (Mateescu et al., Pharmaceutics, 2026). Keep vials in their box and solutions in the dark in the fridge.
What does it mean if GHK-Cu turns green, brown or cloudy?
A shift away from clear blue means the copper’s surroundings have changed, through pH change, oxidation or a competing ligand. Cloudiness, particles or a deposit point to contamination or the wrong diluent. In either case the vial is discarded; causes are covered in GHK-Cu stability.
Is GHK-Cu stable at room temperature?
The complex is chemically robust: in a stress study it was stable in water and pH 4.5 to 7.4 buffers for at least two weeks at 60 °C (Badenhorst et al., Pharm Dev Technol, 2016). Sealed powder tolerates a few days at ambient temperature in transit, but a mixed vial is still kept cold and dark rather than on the bench.
Can GHK-Cu be mixed with other peptides or vitamin C?
Not in the same vial. Copper exchanges quickly between GHK and other ligands (Hureau et al., Chemistry, 2011), and reducing agents such as ascorbic acid can shift copper toward Cu(I), which the complex then releases. Keep GHK-Cu in its own vial of bacteriostatic water; the bench practice is in GHK-Cu handling.
Start from the GHK-Cu overview for the molecular reference and the research background.
Sources: Lau SJ, Sarkar B. Biochem J. 1981 (PMID 7340824). Hureau C et al. Chemistry. 2011 (PMID 21780203). Badenhorst T et al. Pharm Dev Technol. 2016 (PMID 25384620). Mateescu DM et al. Pharmaceutics. 2026 (PMID 42797253).
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
