Symptoms and Diagnosis of Type 2 Diabetes
Symptoms
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 may include:
- increased hunger and thirst
- numbness or tingling in hands or feet
- blurred vision
- frequent gum, skin, or bladder infections
- slow healing of cuts or sores
- feeling tired
- frequent infections
- increased urination
Diagnosis
In the U.S., type 2 diabetes is frequently not diagnosed until many years after it begins, when complications appear. Approximately one-fourth of all people with diabetes may be undiagnosed. The American Diabetes Association recommends that people age 45 and above be tested for diabetes at least every 3 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, regardless of age.
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 for diabetes are the casual plasma glucose test (a blood test taken at any time of day without regard to time since last meal), the oral glucose tolerance test (OGTT: a blood test taken at 2 hours after drinking glucose dissolved in water), and the glycated hemoglobin (A1C).
A diagnosis of diabetes is made if a person has any of the following test results1:
- FPG is 126 mg/dL or higher.
- High blood sugar (hyperglycemia) symptoms exist and casual plasma glucose is 200 mg/dL or higher.
- Plasma glucose is 200 mg/dL or higher at 2 hours during an OGTT.
- A1C is greater than or equal to 6.5%.
If any of these test results occur, 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 sugar (glucose) levels that are higher than normal but not yet high enough to be diagnosed as diabetes. As of 2010, there were at least 79 million people in the United States aged 20 years or older with pre-diabetes.2 A diagnosis of pre-diabetes is made using the FPG test, the OGTT, or the A1C. Depending on which test is used, pre-diabetes is categorized as2:
- Impaired fasting glucose (IFG): FPG is 100 mg/dL to 125 mg/dL.
- Impaired glucose tolerance (IGT): plasma glucose is 140 mg/dL to 199 mg/dL at 2 hours during an OGTT.
- A1C: 5.7% to 6.4%.
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 sugar when you have pre-diabetes, you may be able to delay the onset of type 2 diabetes. 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 Exercise 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—2011. Diabetes Care. 2011;34(suppl 1):S11-S61.
2. Centers for Disease Control and Prevention. National diabetes fact sheet: national estimates and general information on diabetes and prediabetes in the United States, 2011. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 2011. Available at . Accessed October 27, 2011.