describe how glucose tolerance testing can be used to diagnose diabetes.
1 A fasting blood sugar level less than 100 mg/dL (5.6 mmol/L) is normal. 2  A fasting blood sugar level from 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is considered prediabetes. 3  If it's 126 mg/dL (7 mmol/L) or higher on two separate tests, you have diabetes. 4  Oral glucose tolerance test.