Two vials of AHK-Cu went into a serum alongside micro needling, no change seen. But I've injected it under my scalp every day for 4 weeks, using 12.7 mm long 29G insulin syringes, and just recently I spotted fresh hair growth, with strands getting thicker daily. Same protocol as GHK-Cu. Scalp injection of AHK-Cu doesn't seem to be documented anywhere. Injecting it like GHK-Cu was the suggestion I got when I bought it, and injecting under my scalp is my own experiment, so it's no recommendation, just my experience. Not a pleasant feeling either. My wife has used GHK-Cu for 9 weeks and thinks it does nothing, but I can see the fine lines by her eyes and mouth nearly vanished and her skin smoother.