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Why Your Doctor Tests Your Blood Sugar

If you don't have diabetes, and your doctor orders a blood sugar test, what is he or she is checking? In adults, a screening blood sugar test is generally used to determine whether your blood sugar is too high. For adults, having an elevated blood sugar usually won't cause symptoms that may indicate a pending or current problem with type 2 diabetes. Catching and treating type 2 diabetes early is important to prevent complications of diabetes. According to 2011 statistics from the CDC, 18.8 million people, or 8.3 of the U.S. population, have been diagnosed with diabetes, while an additional 7 million Americans have diabetes but have not been diagnosed. The CDC estimates that, in 2010, at least 79 million people in the U.S. ages 20 and older, had prediabetes. In adults, type 2 diabetes accounts for the majority of all diagnosed cases.

Type 2 on the rise

There's an epidemic of type 2 diabetes in America. That epidemic can be controlled if more people begin to pay attention to lifestyle issues. As a society, we eat too much and we exercise too little. Some long-term damage to the body, especially the heart and circulatory system, may already be occurring during prediabetes. People with prediabetes face a great risk for developing type 2 diabetes. Studies have shown that people with prediabetes could prevent the development of type 2 diabetes by making changes in their diet and increasing their level of physical activity.

Many people don't know what type 2 diabetes is or why doctors are interested in their blood sugar levels. In diabetes, the hormone insulin, secreted by your pancreas, isn't used properly. Insulin lets your body use sugar, starches and other food for energy. When there isn't enough insulin or your body's cells are unable to use what is there, blood sugar rises.

In type 2 diabetes, your pancreas either does not secrete enough insulin or insulin isn't used properly by the body's cells (called insulin resistance). Insulin lets your body use glucose, a form of sugar, for energy by transporting glucose into the cells. When there isn't enough insulin or your body's cells are unable to use glucose, blood sugar rises. When blood sugar is consistently elevated, the risk of heart attack and stroke increase by up to four times. It also greatly raises the risk for kidney disease, along with leg amputation from poor circulation, blindness, and other maladies. Type 2 diabetes is usually diagnosed later in life.

In an alarming trend, we're diagnosing many teens with this type of diabetes--something almost unheard of 20 years ago. This is thought to be directly related to obesity, poor diet, and lack of exercise. The American Diabetes Association (ADA) recommends type 2 diabetes screening for children and teens who are overweight and have at least two of these risk factors: a family history of diabetes, in a high-risk ethnic group, or have signs of insulin resistance.

It's always best to catch diabetes before symptoms begin. But watch for these symptoms: fatigue, thirst, frequent urination, sores that don't heal, weight loss, and intermittent blurry vision.

According to the ADA, if you're 45 or older and you don't have risk factors for diabetes, you should get screened every three years. If you have risk factors for diabetes, you may need screening tests more often. If you're under 45, you don't need routine screening unless you are overweight or obese, and have another of the risk factors for diabetes.

Risk factors

Risk factors for type 2 diabetes are:

  • Being older than 45

  • Being overweight or obese (body mass index of 25 or higher)

  • Having parents or siblings who have diabetes

  • High blood pressure (140/90 mmHg or higher in adults)

  • HDL (good) cholesterol of less than 35 mg/dL and/or a triglyceride level of 250 mg/dL or higher

  • A sedentary lifestyle

  • High-risk race/ethnicity (African American, Alaska Native, Hispanic American, American Indian, Asian American, or Pacific Islander)

  • Previously elevated blood sugar test

  • Having diabetes during pregnancy or having a baby weighing more than nine pounds at birth

  • Having polycystic ovarian syndrome (PCOS)

  • Having a history of cardiovascular disease

Diagnosing diabetes

The ADA now recommends the A1C test for use in the diagnosis of prediabetes and diabetes. The A1C (also known as the hemoglobin A1C test), estimates the average blood glucose levels over the preceding 12-month period. An A1C level of around 5 percent is considered normal. An A1C of 6.5 percent or above indicates diabetes.

Although the A1C test is not more accurate than the fasting plasma glucose test (FPG) and the two-hour oral glucose tolerance test (OGTT), it does not require fasting and can be measured at any time of the day. Experts hope the A1C's convenience will result in more people who are at risk for diabetes or prediabetes being tested. This would help reduce the number of people with undiagnosed diabetes in the U.S.

The ADA's Standards of Medical Care in Diabetes (2011) lists the following criteria for the diagnosis of diabetes: an A1C equal to or greater than 6.5 percent; an FPG equal to or greater than 126 mg/dL; a two-hour plasma glucose of greater than or equal to 200 mg/dL during an OGTT; or a person who shows classic symptoms of low or high blood sugar.