The number of Americans with diabetes has grown to nearly 26 million and an estimated one-third of all U.S. adults over 20 now have prediabetes, according to figures released Wednesday by the Centers for Disease Control and Prevention (CDC).

Prediabetes is a condition in which blood sugar levels are above normal, but not high enough to be declared diabetes. It indicates that the person is at high risk of developing type 2 diabetes, heart disease and stroke.

The findings show an increase from a 2008 CDC report on diabetes. Then, the CDC estimated that 23.6 million Americans had the disease and another 57 million adults had prediabetes.

If the trend continues, the CDC projected that as many as one in three US adults will have diabetes by 2050.

The vast majority, more than 90 percent of all cases of diabetes are type 2 diabetes, which can be mitigated through lifestyle changes.

"These distressing numbers show how important it is to prevent type 2 diabetes and to help those who have diabetes manage the disease to prevent serious complications such as kidney failure and blindness," said Ann Albright, director of the CDC's Division of Diabetes Translation. "We know that a structured lifestyle program that includes losing weight and increasing physical activity can prevent or delay type 2 diabetes."

The CDC warns the disease is both deadly and costly. Diabetes is the seventh leading cause of death in the US. The disease raises the risk of heart attack, stroke, high blood pressure, kidney failure, blindness and amputations. Diabetes costs the U.S. more than $174 billion a year, according to CDC estimates.