How is diabetes diagnosed?

This test is often done in the morning before breakfast. Diabetes is diagnosed if the fasting blood sugar level is over 126 milligrams per deciliter (mg/dL). That’s 7 millimoles per liter (mmol/L).

Sugar molecules can bind to the red pigment in your blood known as hemoglobin. Your HbA1c value shows how much of your hemoglobin has been changed in this way. It is a measure of your average blood sugar level over the last 8 to 12 weeks. People with an HbA1c over 6.5% are considered to have diabetes.

Blood sugar levels are also often tested when blood is taken for another reason. In these random tests, levels above 200 mg/dL (11.1 mmol/L) are a sign that you may have diabetes. Then doctors usually recommend that you do a fasting blood sugar test or a glucose tolerance test to find out for sure.

The oral glucose tolerance test (OGTT) measures how well your body can process sugar. It is done if the results of other tests aren’t clear or if you have a high risk of developing diabetes. First, you drink a glass of water with 75 grams of sugar (glucose) dissolved in it. This makes your blood sugar levels rise, but they should go back down quite quickly after that. If they’re still above 200 mg/dL (11.1 mmol/L) after two hours, you’re diagnosed with diabetes.