Classification and diagnosis of diabetes mellitus since 1997 include four types of diabetes mellitus, simplification of the diagnostic criteria for diabetes mellitus to two abnormal fasting plasma determinations and a lower cut-off for fasting plasma glucose to confirm the diagnosis of diabetes mellitus. These changes provide an easier and more reliable means of diagnosing persons at risk of complications from hyperglycemia. Large prospective randomized trials found a correlation between glycemic control and reduction in the progression of chronic complications associated with diabetes. Measurement of glycosylated hemoglobin (HbA1c) remains a gold standard for the assessment of glycemic control in patients with diabetes. Recent investigations have studied the correlations between Hba1c levels, postprandial glucose (PPG) and fasting plasma glucose (FPG).