Yes I know most of the common reasons that people do not tolerate NAC but I would like to start a discussion and maybe someone could mention an effective way to overcome this roadblock in order to boost glutathione. Whenever I supplement with NAC I get muscle tension, pain and excitation with poor sleep quality. The dosage I use is 600mg daily. I have side effects since day 1. -Sulfites overload-sulfur intolerance-transulfuration cycle blockage (solution b1 and molybdenum): I have tried that I can tolerate NAC for one or two days then I have again side effects -Oxalates.... (oxalate stones mimics sulfites and bind to the sulfur receptors and generally block all pathways): I already supplement with the cofactors that break down oxalates for a long time but have seen no change -Heavy metals bound to sulfur (particularly mercury) making it difficult to clear transulfuration pathway. However I can not think how I could overload my body on mercury as I have never had amaglam fillings plus I have used zeolite for detox many times. Heavy metals is a big questionmark for me as I have never been tested for it. -Selenium: I have been supplementing with selinium as well.