I use S-Acetyl-L-Glutathione which is the best form to take because it doesn't get digested or need re-activation which requires cellular energy. It can be purchased as capsules of around 100mg and powder form in various sizes from around 2g to 50 grams but in China it is sold very cheaply but whether it is real I certainly doubt based upon reviews that one person gave to one seller. It's just too cheap to be real IMO.
A milligram digital scale helps or stainless steel scoops which I use for speed 1/64, 1/32, 1/16, 1/8, 1/4 tsp sizes. I usually use 1/8 or 3/16 tsp at most because of the expense.
There is Liposomal Glutathione, Reduced L-Glutathione and S-Acetyl-L-Glutathione which is the best form to use. ME does have such high digestive permeability that even Reduced Glutathione should be absorbed into the blood stream without being digested but it is when it gets into the bloodstream where S-Acetyl-L-Glutathione is of benefit because it doesn't require reactivation and can be used directly by cells.
I have been getting mine from
****Here****