Blood glucose is an important source of fuel for the body. It is the preferred fuel of the brain and working muscles, and under normal circumstances is readily available in the blood. Glucose starts out as carbohydrate in the diet, and it is digested in the small intestines. From there, glucose enters the blood stream where it circulates to the organs and tissues that need it. Glucose levels are normally regulated by the body through a complex relationship between diet, activity and hormones. However, patients with diabetes often have trouble managing their blood glucose levels. If levels remain high over long periods of time, it can result in a number of serious and often life-threatening complications.
Fasting Blood Glucose
Chances are when you have your annual physical examination with your doctor, he'll ask you to arrive at the office having fasted for at least 12 hours. He does this so he can test your fasting blood glucose levels. Fasting blood glucose levels are considered normal glucose levels. Food, exercise and stress can affect the levels. The acceptable fasting blood glucose range in healthy individuals is 70 to 100 mg/dl. If your fasting blood glucose level is higher or lower, it could indicate an underlying disease and may require additional tests.
Oral Glucose Tolerance Test
If your fasting blood glucose results are out of the normal range, your doctor may order an oral glucose tolerance test (OGTT). Oral glucose tolerance tests are the next step in determining whether you have diabetes and will tell your physician if you have any problems metabolizing carbohydrates. After a 12 hour fast, you'll have your blood drawn and tested for glucose. You'll then be asked to drink a beverage that contains 75 to 100 grams of glucose. Your blood will be sampled four or five times over a three-hour period to test how well your body processes glucose. Healthy, disease-free individuals will have glucose levels of less than 140 mg/dl after two hours. If your glucose level is between 140 and 199 mg/dl, you have impaired glucose tolerance. Anything higher than 199 mg/dl could indicate that you have diabetes.
Hemoglobin A1c
One of the best tests for blood glucose is the hemoglobin A1c (HbA1c) test. Unlike fasting or OGTT results that indicate your glucose level at one point in time, the HbA1c measures your average glucose levels over the lifespan of your red blood cells---about 120 days. Normal values of HbA1c are 4 to 6 percent. Values over 6.5 percent could indicate pre-diabetes.
