N-acetyl-L-cysteine and vitamin C are frequently taken together, however, the two supplements should never be taken together. One of the selling points of taking the two supplements together was that N-acetyl-L-cysteine would prevent the oxidation of vitamin C to dehyrdroascorbate which N-acetyl-L-cysteine very effectively does. However dehyrdroascorbate is the form of vitamin C absorbed via glucose transporters. Preventing the oxidation of vitamin C with N-acetyl-L-cysteine is a huge error. There are many grounds for not supplementing N-acetyl-L-cysteine. The high effectiveness of N-acetyl-L-cysteine in preventing oxidation of vitamin C is one.