GHK Cu vs NAD+: Which Longevity Peptide Should You Take or Stack? The Pen: This is why delivery systems matter. For years, peptide therapy relied on lyophilized vials, manual reconstitution, dilution calculations, and insulin syringes. Every step introduced variables, dosing inaccuracies, contamination risk, peptide Injectable GHK Cu: Beginner's Guide to Copper Peptide GHK Cu and Reproductive Health: Mechanisms, Fertility Benefits