Copper Peptides (GHK Cu): Benefits and Side Effects 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. The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline 12 weeks in, and my skin has NEVER looked better! GHK peptides are doing their thing. Alright, I need to give you an updateit's been 12 weeks since I started using GHK Why does Glycyl Histidyl Lysine Copper (GHK Cu) cause pain or discomfort? GHK Cu Copper Peptide: Dosage, Before and After Results, and How It Works Perfect B