The blood sugar levels obtained from this test are put into the following categories: Normal range, if it falls between 4.0 to 5.9 mmol/l (70 to 107 mg/dl). Prediabetes, if the reading is between 6.0 to 6.9 mmol/l (108 to 126 mg/dl). Diagnosis of diabetes, if the reading is more than 6.9 mmol/l (126 mg/dl). Impaired glucose tolerance test: Before conducting this test, the patient is asked to take concentrated amount of glucose and then the doctor measures his or her blood sugar level after two hours.