NEW YORK -- The number of Americans with diabetes has increased again -- now more than 29 million people have the illness.

That’s an increase of about 3 million from three years ago.

In new report released Tuesday, federal scientists calculated that more than 9 percent of Americans have diabetes -- or 1 in 11 people. The report estimates that about a quarter of them haven’t been diagnosed yet and don’t know they have diabetes.

The Centers for Disease Control and Prevention used a 2012 national survey and other data to come up with the new numbers.

Diabetes is a disease in which sugar builds up in the blood. The most common form is tied to obesity, and the number of diabetics has ballooned with the rise in obesity.