What GHK-Cu is
GHK is a tripeptide, glycyl-L-histidyl-L-lysine, present in human plasma at concentrations that decline with age. GHK-Cu is that tripeptide in a 1:1 complex with copper(II), which the histidine imidazole and the terminal amine coordinate with high affinity. The complexed form is the biologically studied one; the free peptide and the complex are not interchangeable.[2]
The visual tell is straightforward: correctly complexed GHK-Cu is a deep blue, and the intensity of that blue is a rough proxy for copper loading. Material that arrives pale, patchy or white has a copper problem regardless of what its purity certificate says about the peptide.

