GHK Cu vs NAD+: Which Longevity Peptide Should You Take or Stack? A lot of people asked how I use GHK Cu (copper peptide) with a pen device, so here's a quick tutorial showing exactly how I do it. In this video I show how The Secret Your Skin Already Knows GHK Cu is not a random combination of letters. It is a naturally occurring copper peptide that helps your skin do what it already knows how How much GHK Cu should I inject daily? GHK Cu (2mg, 60 Capsules) (Copper Tripeptide) USA Made, Third Party Tested