What is prediabetes?
About 41 million Americans between the ages of 40 and 74 have "prediabetes." Prediabetes is a condition that can be considered an early, yet potentially reversible stage of the development of type 2 diabetes. Prediabetes is sometimes called impaired glucose tolerance or impaired fasting glucose (IGT/IFG), depending upon the test that yielded the abnormal result. In prediabetes, a person's blood sugar (glucose) levels are slightly higher than the normal range, but not high enough for a true diagnosis of diabetes. People with prediabetes have a significant risk of developing full-blown diabetes. In the Diabetes Prevention Program study, about 11% of people with prediabetes developed type II diabetes each year during the three year follow-up time of the study. Importantly, people with prediabetes generally have no symptoms of the condition.
Testing for Pre Diabetes
Doctors generally use one of two different blood tests to diagnose diabetes and prediabetes. One is called the fasting plasma glucose test (FPG) in which a person's blood glucose level is measured first thing in the morning before breakfast. The normal fasting blood glucose level is below 100 mg/dl. A person with prediabetes has a fasting blood glucose level between 100 and 125 mg/dl. If the fasting blood glucose level is to 126 mg/dl or above, a person is considered to have diabetes.
The second test used in the diagnosis of diabetes is the oral glucose tolerance test (OGTT), although this test is no longer commonly used as in the past. This test may be used to diagnose gestational diabetes in pregnant women. In this test, a person's blood glucose is measured in the morning after fasting overnight and again two hours after drinking a glucose-rich beverage. The normal value for blood glucose is below 140 mg/dl two hours after the drink. In prediabetes, the two-hour blood glucose is 140 to 199 mg/dl. If the two-hour blood glucose rises to 200 mg/dl or above, a person has diabetes.
The A1c test, or hemoglobin A1c level, is another blood test that measures how much glucose has been sticking to hemoglobin during the past three to four months. Hemoglobin is the substance in the red blood cells that carries oxygen to the cells of the body. The A1C test is important in diabetes and prediabetes as a measure of the glucose control during the prior three months. Normal values for the hemoglobin A1c are 5.6% or below. Values between 5.7% and 6.4% are considered to reflect prediabetes, while values of 6.5% and over are typical for diabetes.
Long-term effects of diabetes and prediabetes
Research has shown that some of the long-term effects of diabetes on the body, such as damage to the heart and blood vessels, can begin even when a person only has prediabetes. Having prediabetes increases your risk of developing cardiovascular disease by about 50% compared to people with normal blood sugar levels.
You won't necessarily know if you have prediabetes, since the condition usually causes no specific symptoms. If you are overweight or have other risk factors for the development of diabetes, your doctor can help you decide if screening for prediabetes is appropriate.
The good news for people with prediabetes is that they can prevent or delay the development of diabetes with lifestyle modifications. Modest weight loss through diet and moderate exercise (such as walking 30 minutes per day, five times a week) can slow the development of diabetes and can even return blood glucose levels to normal in some people with prediabetes. Overweight people who have prediabetes need not achieve their ideal body weight to improve their condition. Studies show that a weight reduction of just 5% to 10% of body weight can improve blood glucose levels. Since you can take measures to reverse the condition, recognition of pre-diabetes is an important step in disease prevention.
Medically reviewed by John A. Seibel, MD; Board Certified Internal Medicine with a subspecialty in Endocrinology & Metabolism
American Diabetes Association. Prediabetes.