There are few causes of persistent hyperglycemia in adults other than diabetes mellitus. Transient hyperglycemia may occur during a severe illness in adults without known diabetes mellitus. This is sometimes referred to as “stress hyperglycemia” and is a consequence of many factors, including increased serum concentrations of cortisol, catecholamines, glucagon, growth hormone, leading to increased gluconeogenesis and glycogenolysis, and insulin resistance.