A copper peptide used for skin rejuvenation, hair growth, and anti-aging. Available as injectable or topical: - Injectable: Common protocol is 2 mg per dose. Some experience emotional/irritability side effects and reduce to 0.5 mg. The "5 days on, 2 days off" protocol originated from medspa scheduling, not science. - Topical: 1 g raw GHK-Cu per 1 oz (30 mL) hyaluronic acid serum. - Burning on injection: dilute more and/or let the syringe reach room temperature before injecting.