However, as reassuring as all of this is, there are a couple of things to remain mindful of: Copper toxicity Because GHK-Cu contains copper, it does pose a potential risk of copper toxicity,12 the symptoms of which include abdominal pain, vomiting, chest pain, chills, cough, fever, general weakness, anemia, burning sensations, tremors, and a metallic taste in the mouth.13 The risk is small, as the concentrations of copper in the peptide are typically well within safe parameters, but its good to be aware of it
Opin Microbiol 2020, 55, 1725
There are quite a few people who just are not able to get enough vitamin B12 without receiving it through regular injections for a multitude of reasons, most often including dietary restrictions or medical conditions
10.1093/mtomcs/mfab046