Pre-diabetes may be defined either by an impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). The presence of either finding is associated with a higher risk for the future diagnosis of diabetes.
An impaired fasting glucose level is a fasting plasma glucose from 100 to 125 mg/dL (5.6 to 6.9 mmol/L).
where:
• The lower cutoff has been decreased over time (it was 110 mg/dL in 1997).
An impaired glucose tolerance is a 2 hour plasma glucose of 140 to 199 mg/dL (7.8 to 11.0 mmol/L) following an oral 75 g glucose load (oral glucose tolerance test).
A positive test should be repeated on another day before the diagnosis of prediabetes is made.
The oral glucose tolerance test is not recommended for routine clinical use but may be helpful in patients with an uncertain diagnosis. It must be performed correctly to allow for an accurate diagnosis.
In the past glycosylated hemoglobin A1c was not recommended for making the diagnosis of diabetes. In 2008 an International Expert Committee recommended that a glycosylated hemoglobin A1c >= 6.5% be used as a criterion for the diagnosis of diabetes. A glycosylated hemoglobin A1c from 6.0 to 6.4% indicates a patient at increased risk for developing diabetes.
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