Blood sugar levels are tested by placing a small amount of blood on a testing strip and feeding it into a glucose meter, notes Mayo Clinic. The glucose meter processes the blood and indicates the amount of blood sugar found in it.
The most accurate readings are obtained using blood from a finger, according to Mayo Clinic. Patients should wash their hands and then insert a test strip into the glucose meter. They should then prick the side of the finger near the nail to minimize soreness in other areas, notes the American Diabetes Association. Patients should hold the drop of the blood to the test strip, which returns blood sugar results in approximately 15 seconds.