Diabetes mellitus is an increasingly prevalent condition.[1][2] This condition is characterized by hyperglycemia. The two main types of diabetes are type 1 diabetes mellitus and type 2 diabetes mellitus, with type 2 diabetes accounting for 90% of all cases. Other types of diabetes mellitus include gestational diabetes, drug-induced diabetes, and monogenic diabetes. Complications of diabetes mellitus affect all body systems and can include lethal consequences. The purpose of this article is to review nursing diagnoses, causes, risk factors, assessment, evaluation, medical management, nursing management, and other aspects of importance to nurses.