Diabetes, or high blood sugar, was the seventh highest cause of death in the United States in 2006 and affects 23 percent of people over age 60, the American Diabetes Association (ADA) reports. Early diagnosis of diabetes is essential for treating the disease before damage is done to major organs. Diabetes is the leading cause of new cases of adult blindness and kidney disease requiring transplantation. Diabetes increases the risk of stroke and heart disease. There are several blood tests used to diagnose diabetes.
Fasting Blood Glucose
Fasting blood glucose, or sugar, is a blood test taken after fasting for at least eight hours. No food or drink except water is allowed before the test, or the results will not be accurate. It's usually done first thing in the morning. Fasting blood sugar levels should be between 60 and 99 milligrams per deciliter (mg/dl). A person is not diagnosed with diabetes unless he has fasting blood glucose of 126 mg/dl on two separate readings done on different days, the Diabetes Teaching Center at the University of California, San Francisco states. Impaired fasting glucose levels are from 100 to 125 mg/dl and are considered to be indicative of possible diabetic disease in the future; this is referred to as pre-diabetes.
Oral Glucose Tolerance Test
The glucose tolerance test assesses blood levels after the administration of a glucose solution. The test takes up to three hours. After fasting for eight hours, you have blood drawn. You then drink a solution containing 75 grams of glucose, or sugar. Two hours after drinking the glucose, blood is drawn again. A blood glucose level two hours after drinking the glucose solution should be less than 140 mg/dl. Levels of 140 to 199 mg/dl indicate pre-diabetes, and levels greater than 200 mg/dl are diagnostic for diabetes.
Hemoblobin A1C
Hemoglobin A1C is different than other types of diabetes diagnostic testing because it doesn't measure the exact amount of glucose present at a given time. Rather, the test measures average blood sugars over a three-month period. The A1C measurement is controversial for use in diagnosing diabetes because factors such as anemia or treatment with drugs that stimulate new red blood cell production may affect the results, the Diabetes Teaching Center warns. However, the ADA recommends use of the test to diagnose diabetes and pre-diabetes. A normal A1C level is around 5 percent, and levels of 5.7 to 6.4 percent suggest pre-diabetes. Levels over 6.5 percent are diagnostic for diabetes, the ADA states. A1C levels can be drawn at any time; fasting is not required.
References
- Diabetes Education Online: University of California, San Francisco; Diagnosing Diabetes
- Milton S. Hershey Medical Center: Glucose Tolerance Test
- American Diabetes Association: New Clinical Practice Recommendations Promote A1C as Diagnostic Test for Diabetes
- American Diabetes Association: Diabetes Statistics
