Many aren't aware they have diabetes
The disease can cause blindness, kidney failure and amputations in adults.
Even as more people are diagnosed, about one-third of Americans age 20 and older who have diabetes still don't know they have it, according to a study based on government health surveys.
Researchers from the National Institutes of Health and the federal Centers for Disease Control and Prevention report that overall incidence of diabetes among adults rose to 6.5 percent when a survey that included a physical exam and blood test was done between 1999 and 2002.
That's up from 5.1 percent of adults in 1988-94, when the last round of similar tests was done.
But the study, published in the June issue of the journal Diabetes Care, found that the share of adults who were identified as having diabetes through the surveys, but did not know it, remained the same at 2.8 percent.
"The study updates and generally corroborates earlier analyses that were based on two years of [survey data]," said Catherine Cowie, a researcher at the National Institute of Diabetes and Digestive and Kidney Diseases who led the study.
"We're seeing a rising prevalence of diagnosed diabetes that is not substantially offset by a drop in the rate of undiagnosed cases."
Also during both survey periods, about 26 percent of the adults tested continued to have impaired fasting glucose (IFG), a form of pre-diabetes in which blood-sugar levels are high but not yet at the level considered diabetic.
Diabetes is actually a group of diseases marked by high levels of blood glucose caused by defects in insulin production, insulin action or a combination.
The disease is the most common cause of blindness, kidney failure and amputations in adults, and a major contributor to heart disease and stroke.
Pre-diabetes, which usually has no symptoms, is serious because many people with the condition go on to develop problems processing sugars in the next 10 years, and even those who don't get those problems have elevated heart and blood vessel disease risks.
"These findings are extremely important," said Dr. Stuart Weiss, a diabetes specialist at New York University Medical Center who was not involved in the study. "The number of people with diabetes is exceeded only by the number of people with diabetes who are in denial.
"People hate being diagnosed with diabetes because it's all about lifestyle. When you have diabetes, you must change the way you live."
People with pre-diabetes can often prevent or delay the onset of disease by losing a modest amount of weight from cutting calories and boosting exercise levels.
The researchers also found that 22 percent of people age 65 and older had diabetes, and nearly 40 percent had impaired fasting glucose, which becomes more common as people age. Generally, anyone 45 and older should talk to a doctor about being tested for diabetes or pre-diabetes. People who are younger than 45, overweight and have risk factors such as high blood pressure, high cholesterol or a family history of diabetes should also ask about screening, experts say.
Although diabetes is about twice as common in non-Hispanic blacks than in non-Hispanic white adults, the surveys showed that diabetes and IFG were most likely to go undiagnosed in white men.