Will taking 600mg of nac daily effect liver enzyme tests?

Depends.: It has been reported to affect liver enzymes in a patient with cystic fibrosis. As with any supplements, benefit is iffy, depending on what you are using it for. If not prescribed or recommended by doc, be leery of wasting your money. Many supplements have not been studied in sufficient detail for a long enough time to know for sure if they are safe. See http://tinyurl.com/ng3ajr4