Alcohol dehydrogenase (AD, EC 1.1.1.1 ) activity in serum markedly increases in cases of hypoxic hepatic injury and acute hepatitis. Furthermore, AD can reduce oxidized coenzyme NAD+ to NADH even without substrate such as ethanol. Therefore, AD interferes in clinical chemical tests using the reducing reaction of coenzyme NAD+. We found that AD caused a false positive in serum glucose determination using an enzymatic procedure (hexokinase/glucose-6-phosphate dehydrogenase/NAD+ coupled assay) and increased the blank value of the sample on lactate dehydrogenase (LD) assay using the method recommended method by JSCC (Japanese Society of Clinical Chemistry). We should approve the correction of sample blank reaction in LD activity assay using the method recommended by JSCC as well as the IFCC (International Federation of Clinical Chemistry) method. Also, we should adopt the enzymatic procedures using the reducing of coenzyme NADP+ or without the influence of AD.