NEW YORK -- The CDC says more than one in three Americans have blood-sugar levels that raise their risk of developing the disease.
Researchers at UCLA estimate nearly half of all adults in California have prediabetes or undiagnosed diabetes: 46 percent of all adults, and 33 percent of young adults between the ages of 18 and 39.
"The rates are very high, surprisingly high," researcher Susan Babey, who coauthored the report, told CBS News. "We're very concerned about the rates among the young adults because of their increased risk of developing type 2 diabetes, which sets them on this path for some serious complications in the future."
Complications include blindness, heart and kidney disease and premature death. Without intervention, about 70 percent of those with prediabetes eventually develop diabetes.
With intervention, it doesn't have to progress to the full-blown disease, according to Dr. Jacqueline Lonier of the Naomi Berrie Diabetes Center at New York Presbyterian.
"The most effective way to prevent progression of prediabetes to diabetes is through diet and exercise -- regular activity, watching carbohydrate intake," Lonier said.
Paul Healy, 52, was diagnosed with prediabetes in 2010 and then diabetes. Since then, he has changed his diet and lost 32 pounds.
"Part of what happened, when I was diagnosed, is that I was really in denial about it," Healy said. "So, it took me awhile to really get my blood sugars under the control and learn how to say no."
The CDC estimates 90 percent of people with prediabetes don't know they have it. But a simple blood test could quickly make the diagnosis.
That's crucial because, more than half the time, diet and exercise can prevent prediabetes from progressing to diabetes.