Classification and Diagnostic Criteria

Diabetes mellitus comprises a heterogeneous group of disorders characterized by high blood glucose levels. Four major types of diabetes have been defined: insulin-dependent diabetes mellitus (IDDM), non-insulin-dependent diabetes mellitus (NIDDM), gestational diabetes mellitus (GDM), and diabetes secondary to other conditions. IDDM characteristically presents with prominent diabetes symptoms and extreme hyperglycemia. NIDDM can be diagnosed by the presence of the classical signs and symptoms of diabetes together with unequivocally elevated blood glucose levels; by fasting plasma glucose (FPG) ≥140 mg/dl; or by venous plasma glucose ≥200 mg/dl at 2 hours after a 75-g oral glucose challenge. Criteria for GDM vary but require an oral glucose challenge and measurement of post-load plasma glucose.