From my experience with GHK-CU 200mg ZPHC, the dosing really depends on your skin’s sensitivity and goals. I initially used a diluted concentration by adding 5 mL of bacteriostatic water to the lyophilized GHK-Cu vial, which set me at 40 mg/mL — on a 100-unit insulin syringe, 1 unit equals roughly 0.4 mg of GHK-Cu. This dosing seemed gentle enough to avoid irritation while supporting skin firmness and texture improvement after a few weeks of regular application. I’ve tried ramping up to 10 mg doses several times a week, and the collagen production effects felt more noticeable. However, for beginners, it’s safer to start with 1 to 2 mg doses until you see how your skin reacts. The product’s quality and proper storage—keeping it refrigerated and protecting it from light—also play a big role in effectiveness. The batch I got was authentic and batch-verified, which gave me confidence. Overall, mixing and dosing require a careful balance tailored to your individual needs and, frankly, some trial and error.