- A fasting blood glucose test. This test is performed after you have fasted (no food or liquids other than water) for eight hours. A normal fasting blood glucose level is less than 110 mg/dl. A diagnosis of diabetes is made if your blood glucose reading is 126 mg/dl or higher. (In 1997, the American Diabetes Association lowered the level at which diabetes is diagnosed to 126 mg/dl from 140 mg/dl.)
- A "random" blood glucose test taken at any time. A normal blood glucose range is in the low to mid 100s. A diagnosis of diabetes is made if your blood glucose reading is 200 mg/dl or higher and you have symptoms of disease such as fatigue, excessive urination, excessive thirst or unplanned weight loss.
- Another test called the oral glucose tolerance test may be performed instead. For this test, you will be asked, after fasting overnight, to drink a sugar-water solution. Your blood glucose levels will then be tested over several hours. In a person without diabetes, glucose levels rise and then fall quickly after drinking the solution. In a person with diabetes, blood glucose levels rise higher than normal and do not fall as quickly. A normal blood glucose reading two hours after drinking the solution is less than 140 mg/dl, and all readings between zero to two hours are less than 200 mg/dl.
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