There are more than 20 million people in the United States who have diabetes; 14 million are diagnosed and an estimated 6 million who are unaware that they have diabetes. Thus, nurses in every setting are interacting with patients who have diabetes. Those nurses who are knowledgeable about diabetes can play a major role in reducing the damage that diabetes causes by educating patients and helping them identify the important aspects of managing their disease. In this article, a brief overview addresses the two major types of diabetes and the serious implications of uncontrolled diabetes. A review of selected antidiabetic medications identifies the mechanisms of action and potential side effects pertinent to each medication. Laboratory tests used to identify and monitor diabetes are also addressed.