NBC News - More than 29 million American adults have diabetes, and a quarter of them don’t even know it, a new report shows.

That’s up from 26 million in 2010, the Centers for Disease Control and Prevention says, and represents more than 9 percent of the population.

And another 86 million — a third of the adult population — are headed down the road to diabetes, with blood sugar levels high enough to mark them as pre-diabetic.

“These new numbers are alarming and underscore the need for an increased focus on reducing the burden of diabetes in our country,” said Ann Albright, who directs the division of diabetes translation at the CDC. “Diabetes is costly in both human and economic terms. It’s urgent that we take swift action to effectively treat and prevent this serious disease.”

The CDC makes its estimates based on a national sample of Americans, who are asked whether they have been diagnosed with diabetes and who also give blood samples.

They are not asked specifically about what type of diabetes, but the vast majority have type 2 diabetes, which is often caused by poor diet and a lack of exercise.

Type 1 diabetes is usually diagnosed in childhood and is an autoimmune disease in which the body mistakenly attacks the pancreatic cells that make insulin. It affects about 5 percent of all people with diabetes.

The CDC says that in 2012, 1.7 million adults were newly diagnosed with diabetes. More than 200,000 children and teenagers have diabetes of any kind, type 1 or type 2.

The CDC says diabetes and its related complications rack up $245 billion in medical costs, lost work and wages. That’s up from $174 billion in 2010.

Diabetes is caused when the body cannot process blood sugar properly. High glucose levels damage tiny blood vessels, which in turn can lead to blindness, heart disease, stroke, kidney failure. People can lose toes, feet or legs to amputation.

Diabetes directly kills more than 71,000 people a year, according to the American Diabetes Association.