best topical ghk-cu peptide Copper Serum REMEDY Copper Peptide Complex Advanced
Description
injections of doses of 20, 100, or 500 g/kg to rats, the peak time (Tmax) of each dose was 3 min, while the Cmax of each dose was equivalent to 12.3, 48.9, and 141 ng/mL, respectively

So, you would need to inject 0.5 milliliters of the solution to deliver 500 mcg of vitamin B-12

Independent third-party research on reptides.co not affiliated with Polaris Research

(1986) Oxygen uptake and glutamate dehydro-genase release in isolated renal tubules from rat kidney