The incidence of diabetes is increasing as more people become overweight or obese. According to the U.S. Centers for Disease Control and Prevention, the number of new cases of diabetes that were diagnosed in the U.S. each year tripled from 1980 to 2009, reaching 1.8 million new cases in 2009. Since early diagnosis is critical for avoiding or delaying the complications of diabetes, the American Diabetes Association updated its diagnostic criteria in 2010.
Insulin is the Key
Your cells need glucose for fuel. Whenever you consume a meal, the carbohydrates in your food are converted to glucose, the glucose is absorbed into your bloodstream and -- with the help of insulin secreted from your pancreas -- driven into your cells where it can be metabolized immediately or stored for future use. If you don't make enough insulin, or if your cells do not respond to the insulin that you do make, your blood glucose rises higher than it should.
Changing Diagnostic Criteria
For decades, physicians have used blood glucose levels to not only diagnose diabetes, but to adjust treatment for individual diabetics. Over the years, the criteria for diagnosing diabetes tightened as new information indicated that too many people were being diagnosed after their disease had gained a foothold. In 1997, the first Expert Committee on the Diagnosis and Classification of Diabetes Mellitus abandoned previous criteria and instituted new standards based on clinical data.
Diabetic Glucose Levels
According to work published in the April 2010 "American Family Physician," the diagnostic blood glucose levels established in 1997 remained unchanged in 2010. If you exhibit a random blood glucose reading -- one measured in a non-fasting state -- above 199mg per deciliter, you probably have diabetes. Likewise, a reading over 199mg/dL after a two-hour oral glucose tolerance test, or OGTT, means you are diabetic. A fasting glucose above 125mg/dL also establishes the diagnosis. A new criterion that was established in 2010 allows physicians to diagnose diabetes in anyone with an A1C level over 6.4 percent. An A1C measures your average blood glucose level over the previous 90 days.
Normal Glucose Levels
Extrapolating from the ADA's criteria, you might assume that normal values are signified by a fasting glucose below 125, a random glucose under 200 or a two-hour OGTT reading under 200mg/dL. However, an additional "at risk" category, formerly called "prediabetes" or "borderline diabetes," includes individuals whose fasting glucose values, two-hour OGTT readings and A1C values range from 100 to 125mg/dL, 140 to 199mg/dL or 5.7 to 6.4 percent, respectively. Thus, true "normals" are indicated by a fasting glucose less than 100, a two-hour OGTT reading below 140 and an A1C less than 5.7. Random glucose readings are less sensitive indicators of diabetes, but such readings should consistently fall below 140mg/dL to be called "normal."
The Changing Face of Diabetes
Type 2 diabetes is a disease that develops over many months or even years. The concept that you are non-diabetic on one day and diabetic on the next is inaccurate. Physicians have changed their approach to screening in order to detect diabetes -- and identify people who are at risk -- long before its complications develop. Toward that end, you might get screened for diabetes if you are overweight or if you have high blood pressure or elevated lipid levels, because these conditions have been linked to metabolic syndrome, which increases your risk for diabetes.
