Criteria for the diagnosis of DM include one of the following:

• Fasting plasma glucose ≥7.0 mmol/L (≥126 mg/dL)
• Symptoms of diabetes plus a random blood glucose concentration ≥11.1 mmol/L (≥200 mg/dL)
• 2-h plasma glucose ≥11.1 mmol/L (≥200 mg/dL) during a 75-g oral glucose tolerance test.
• Hemoglobin A_1c >6.5%

These criteria should be confirmed by repeat testing on a different day, unless unequivocal hyperglycemia is present.

Two intermediate categories also have been designated:

• Impaired fasting glucose (IFG) for a fasting plasma glucose level of 5.6-6.9 mmol/L (100-125 mg/dL)
• Impaired glucose tolerance (IGT) for plasma glucose levels of 7.8-11.1 mmol/L (140-199 mg/dL) 2 h after a 75-g oral glucose load

Individuals with IFG or IGT do not have DM, but are at substantial risk for developing type 2 DM and cardiovascular disease in the future.

Screening with a fasting plasma glucose level is recommended every 3 years for individuals over the age of 45, as well as for younger individuals who are overweight (body mass index ≥25 kg/m²) and have one or more additional risk factors (Table 173-1).

The metabolic syndrome (also known as insulin resistance syndrome or syndrome X) is a term used to describe a commonly found constellation of metabolic derangements that includes insulin resistance (with or without diabetes), hypertension, dyslipidemia, central or visceral obesity, and endothelial dysfunction and is associated with accelerated cardiovascular disease (Chap. 118. Metabolic Syndrome).