The American Diabetes Association recommends three ways to diagnose diabetes in nonpregnant adults:
fasting plasma glucose =126 mg/dL (=7.0 mmol/L), or
symptoms of hyperglycemia and a casual plasma glucose concentration =200 mg/dL (=11.1 mmol/L), or
2-hour plasma glucose =200 mg/dL (=11.1 mmol/L) after a 75-gram oral glucose tolerance test
In the absence of unequivocal hyperglycemia, these criteria should be confirmed by repeat testing on a different day.
Fasting plasma glucose is the preferred diagnostic test because of its ease of use, acceptability to patients, and lower cost. The use of the A1C for diagnosing diabetes is not recommended at this time.
American Diabetes Association. Standards of medical care in diabetes—2009. Diabetes Care. 2009;32(suppl 1):S13-S61.
