By Lead writer: Eric Metcalf
Updated February 29, 2016

Prediabetes is an incredibly common condition in which blood sugar is higher than it should be, but isn't quite high enough to be type 2 diabetes. An estimated 84 million people in the United States, including more than a third of adults 18 and older and nearly half of adults 65 and up, are thought to have prediabetes. If you have prediabetes, you don't have diabetes.

But don't relax just yet. Prediabetes is a serious condition in and of itself. Prediabetes is linked to a great risk of heart disease and stroke due to the chronic damage that elevated blood sugar can cause to your heart and blood vessels.

Studies have show that most people with prediabetes—–but not all—will have type 2 diabetes within a decade. On the upside, taking steps to lower your blood sugar now can help prevent or delay the onset of full-blown diabetes. If you lose 5 to 7 percent of your body weight through lifestyle changes, you can considerably diminish your likelihood of developing type 2 diabetes.
Impaired glucose tolerance and impaired fasting glucose
Prediabetes is characterized by two conditions: impaired glucose tolerance and impaired fasting glucose. If you have one or both conditions, you are considered prediabetic. (Both tests can also be used to diagnose diabetes.)

In both cases, your blood sugar is elevated, but falls short of diabetes. For example, if your blood sugar is between 140 and 199 mg/dl two hours after an oral glucose test, you have impaired glucose tolerance (a diabetes diagnosis requires a blood sugar of 200 mg/dL or higher after an oral glucose test).

If you had a blood sugar between 100 and 125 mg/dl after an overnight fast, you would have impaired fasting glucose (a diabetes diagnosis would be 126 mg/dl or higher).

"Now, neither of those conditions are actually diabetes," says Gerald Bernstein, MD, director of the diabetes management program at the Gerald J. Friedman Diabetes Institute at Beth Israel Medical Center in New York City. "But they put you at risk for diabetes."

Silver lining: A chance to change
Hearing you have prediabetes isn't great. But there is a silver lining. If you make changes in your diet, increase exercise, and shed weight, you may be able to prevent or delay diabetes.

"There are also medications that we can give to folks with prediabetes that decrease the likelihood that they'll develop full-blown diabetes," says William Bornstein, MD, an endocrinologist at the Emory Clinic in Atlanta. One drug that can help prevent diabetes is metformin.

By the time most people are diagnosed with type 2 diabetes, the insulin-producing cells of the pancreas have lost 50% of their ability to function, says Nadine Uplinger, the director of the Gutman Diabetes Institute at the Albert Einstein Healthcare Network in Philadelphia. That's why they may eventually need to take insulin injections to treat their blood sugar.

If prediabetes is picked up by routine tests in a doctor's office—as it often is—it's an opportunity for patients to possibly prevent or delay damage to those cells.

When he thinks back, Anil Verma suspects he probably had diabetes or prediabetes for several years before he was diagnosed with type 2 diabetes in May 2005. The 38-year-old Seattle-area resident had fatigue and noticed that he was healing slower. But even though both of his parents have type 2 diabetes, Verma thought he was too young to have developed the disease.

He's made big changes in his eating and exercise habits to control his diabetes, but he wishes he'd changed his lifestyle sooner.

"If I'd found out earlier, I could have stopped it or at least slowed it down. If you can catch it when you're prediabetic and lose the weight, you don't end up being diabetic. That's what I tell people now—catch it before it becomes a problem," he says.