Symptoms and Diagnosis of Type 2 Diabetes

In its early stages, type 2 diabetes often has no symptoms. When symptoms do occur, they may come on gradually and be very subtle. They include:

• feeling tired
• dry, itchy skin
• frequent infections

If you have one or more of these symptoms, see your healthcare provider right away.

Diagnosis

In the U.S., type 2 diabetes is frequently not diagnosed until many years after it begins, when complications appear. Approximately one-third of all people with diabetes may be undiagnosed. The American Diabetes Association (ADA) recommends that people age 45 and above be tested for diabetes at least every three years. Adults who are overweight or obese and who have one or more additional risk factors for diabetes should also be tested at least every 3 years.

The preferred test for diagnosing type 2 diabetes is the fasting plasma glucose (FPG) test.¹ This blood test requires fasting (no food or drink except water) for at least 8 hours and is usually done in the morning. Other tests are the casual plasma glucose test (a blood test taken at any time of day without regard to time since last meal), and the oral glucose tolerance test (OGTT; a blood test taken at 2 hours after drinking glucose dissolved in water).

A diagnosis of diabetes is made if a person has any of the following test results¹:

• FPG is 126 mg/dl or higher; or
• Diabetes symptoms exist and casual plasma glucose is 200 mg/dl or higher; or
• Plasma glucose is 200 mg/dl or higher at 2 hours during an OGTT

If any of these test results occurs, testing should be repeated on a different day to confirm the diagnosis.

What is pre-diabetes?

Before people develop type 2 diabetes, they almost always have "pre-diabetes" — blood glucose levels that are higher than normal but not yet high enough to be diagnosed as diabetes. There are 54 million people in the United States who have pre-diabetes.² A diagnosis of pre-diabetes is made using the FPG test or the OGTT. Depending on which test is used, pre-diabetes is categorized as either impaired fasting glucose (IFG) or impaired glucose tolerance (IGT):

• IFG: FPG is 100 mg/dl to 125 mg/dl
• IGT: plasma glucose is 140 mg/dl to 199 mg/dl at 2 hours during an OGTT

Recent research has shown that some long-term damage to the body, especially the heart and circulatory system, may already be occurring during pre-diabetes. Research has also shown that if you take action to manage your blood glucose when you have pre-diabetes, you can delay or prevent type 2 diabetes from ever developing. Much of the same advice for good nutrition and physical activity that is given to patients who have diabetes can benefit people with pre-diabetes. See our Nutrition and Fitness section of this website to begin learning about the positive steps you can take.

References
1. American Diabetes Association. Standards of medical care in diabetes. Diabetes Care. 2008;31(suppl 1):S12-S54.
2. ADA National Diabetes Fact Sheet, 2005. Available at http://www.diabetes.org/diabetes-statistics.jsp. Accessed March 17, 2008.