A normal range for a healthy person's glucose level is anywhere between 70 mg/dL and 99 mg/dL in the morning, after fasting for 8 hours through the night, and less than 140 mg/dL 2 hours after eating. Glucose levels increase and decrease depending on what has been consumed and what kind of activities have been performed, as noted by Virginia Mason.
A person is diagnosed with diabetes if two consecutive glucose tests, performed after fasting, are 126 mg/dL or higher. If any glucose test, whether fasting or not, measures higher than 200 mg/dL, then diabetes is diagnosed. Also, any 2-hour oral glucose tolerance test that measures higher than 200 mg/dL will result in a positive diabetes diagnosis.
The A1c test can also be performed to diagnose diabetes. This particular test averages the blood sugar levels for 3 months. If this test results in 6.5 percent or higher, then the patient is diagnosed with diabetes.
Diabetes is not always overly evident. Although most patients with diabetes experience fatigue, excessive thirst and urination or unexplained weight loss, a patient can also be diagnosed with diabetes without any of these symptoms.
Pre-diabetes can be diagnosed for a patient who has a fasting glucose level between 100 mg/dL to 125 mg/dL, an A1c level between 5.7 and 6.4 percent or any blood glucose level 140 mg/dL and 199 mg/dL.