This is a very interesting article, please read:
"The best way to judge whether your blood sugar is really under control is with a blood test called the glycosylated haemoglobin level, or the HbA1C test, which shows the average blood sugar level over the previous three months. A 'healthy' reading is between 4 to 5.6; above 6.5 confirms diabetes. Your results should always be 7 or less."