Alimentary Pharmacology & Therapeutics, 17 (4), 595-601
Others photograph defined scalp areas and count visible hairs
It's a relatively high amount for a supplement to have, but it shouldn't be a problem for most people since the maximum per-day allowance for adults is 400mcg.34 That said, you may want to avoid Doctor's Best Glutathione + Milk Thistle if you take another supplement that includes selenium or eat a lot of selenium-rich foods (e.g., Brazil nuts, tuna)
A COA indicating 99% purity by HPLC means that 99% or more of the peptide content is the correct GHK-Cu sequence, with minimal contaminants
Also providing your body with enough cysteine is key so the amino acids absence doesnt slow production
The FDA has granted Generally Recognized as Safe (GRAS) status to glutathione when used in food products