Glucose Test

Your doctor will test your blood sugar levels for signs of diabetes. A doctor will administer more than one test to help diagnose diabetes. Two or more glucose tests are peroformed before confirming a diabetes diagnosis. The three most common glucose tests are; the random blood sugar test, the oral glucose tolerance test and the fasting plasma glucose test.

Your blood sugar is usually highest after you eat and lowest after you have not eaten for 8-10 hours. Upon awakening, most people have blood glucose levels between 70 and 110 milligrams of glucose per deciliter of blood (mg/dL). After eating a large meal, a person's blood sugar will rise, but usually not above 140 mg/dL. People with untreated diabetes will generally have higher blood sugars after fasting and after eating.

The three most common glucose tests:

• random blood sugar test
• oral glucose tolerance test
• fasting plasma glucose test

Random blood sugar test
Diabetes is often diagnosed during routine physical exams when blood is drawn for other tests. Since you don't necessarily fast before these physical exams, you may have just eaten and your blood sugar may be high. Even so, it shouldn't be higher than 200 mg/dL. If your random blood glucose is higher than 200 mg/dL, your doctor will probably suspect diabetes and may want to give you a fasting plasma glucose test.

Oral glucose tolerance test
During this test, a person consumes a drink containing glucose dissolved in water. Blood is then drawn in timed intervals over a three-hour period. If plasma glucose levels rise more than expected, the person is diagnosed with diabetes. This test is often used to check pregnant women for gestational diabetes. It is rarely used to diagnose diabetes in other patients, because it is cumbersome and time-consuming.

Fasting plasma glucose test
Many doctors recommend using a fasting plasma glucose test to diagnose diabetes. Before taking this test, you cannot eat anything for 8 to 10 hours. Blood will be drawn from a vein in your arm and sent to a laboratory for testing. If your fasting blood glucose is 126 mg/dL or higher, your doctor will probably diagnose you with diabetes.