Copper Tripeptide (GHK Cu) for Advanced Skincare & Haircare Formulatio Can Copper Peptide Ghk Cu Powder Reduce Hyperpigmentation? Hongda Phytochemistry 7 days on GHK Cu. Here's my honest update. I'm not going to hype this up because the real results don't even start until week 46. But something is already happening. 7 days on GHK Cu. Here's my honest update. I'm not going to hype this up because the real results don't even start until week 46. But something is already happening.