Three tests can be used to find out if you have prediabetes: the fasting plasma glucose test (FPG), the oral glucose tolerance test (OGTT), and the hemoglobin A1C (A1C). The FPG is done after you fast, or go without food, for eight hours. A normal fasting blood sugar level is less than 100 mg/dL. If you have the FPG test, prediabetes is a blood sugar level of 100 mg/dL to 125 mg/dL. Diabetes is a fasting blood sugar level of 126 mg/dL or greater on two or more separate occasions. The OGTT is done after eight hours of fasting and two hours after you drink a sweet beverage. If you have the OGTT, prediabetes is a blood sugar level of 140 mg/dL to 199 mg/dL. Diabetes is a blood sugar level of 200 mg/dL or greater. The A1C is a blood test. It measures your average glucose level in your blood over a period of three months. You don't need to fast before the blood test is done. You may be considered to have prediabetes if your A1C result is between 5.7 and 6.4 percent, depending on the lab running the test. An A1C of 6.5 percent or higher can be used to diagnose diabetes.

The actual span of time can vary, based on how physically active you are. If you are overweight, you can actually head off diabetes by losing weight, says the American Diabetes Association (ADA). If you lose 5 to 10 percent of your body weight and begin exercising for 30 minutes every day, you can greatly reduce your risk for developing type 2 diabetes. Be sure to check with your health care provider before beginning an exercise program. Other ways to help prevent prediabetes are to control your cholesterol levels and blood pressure. If you smoke, quit smoking.

People with prediabetes are 1.5 times more likely to develop heart disease than those who have normal blood sugar levels, according to the ADA. A person with diabetes is two to four times more likely to develop heart disease.

Too much body fat can make your body less able to use insulin properly, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Your body then makes more insulin but eventually can't keep up with the demand. The extra blood sugar then builds up in the bloodstream. Exercise has the opposite effect of too much fat. It helps the insulin in your body work more efficiently.

People with prediabetes usually have no symptoms. The only way to know if you have prediabetes or diabetes is to have a blood test. Talk with your health care provider if you think you need a test for this condition.

Anyone age 45 or older should be tested for diabetes, says the NIDDK. Because your risk rises as you get older, talk with your health care provider about testing if you are 45 or older. If you are younger than 45, you should be tested if you are overweight and at least one of these describes you: a family history of diabetes; low HDL cholesterol levels and high triglyceride levels; high blood pressure; a history of diabetes during pregnancy or a baby born weighing more than 9 pounds; or a member of a minority group that includes African-American, American Indian, Hispanic American, or Asian American/Pacific Islander.

If either diabetes test is positive, your health care provider may order a more complicated test to confirm the diagnosis.