The number of undiagnosed cases of diabetes in the U.S. may be lower than government estimates. A study from the Johns Hopkins Bloomberg School of Public Health found that overall cases of undiagnosed diabetes were significantly less than reported. 

It’s believed this improvement in cases is due to better detection of type 2 diabetes in the U.S., however, disparities remain in certain population subgroups. Researchers found that 9.5 percent of diabetes cases were undiagnosed, far below initial government figures of 20 percent to 30 percent. 

“Our findings suggest that the true figure is much lower and that providers in the U.S. are doing a good job overall with diabetes screening and diagnosis,” said study senior author Elizabeth Selvin, PhD, professor in the Bloomberg School’s Department of Epidemiology. “Nonetheless, undiagnosed diabetes remains high in some subgroups, indicating that there’s still a long way to go.”

Undiagnosed diabetes was found to be more prevalent among patients with Mexican or Asian American ancestry. It was also found that patients with more than a year between health care visits were also more likely to have undiagnosed diabetes. 

“It’s a real concern that certain populations are being missed by the health care system. This is likely a major reason why undiagnosed diabetes remains high in these groups,” said Michael Fang, PhD, assistant professor in the Department of Epidemiology at the Bloomberg School and the paper’s first author.

Approximately 14 percent of U.S. adults have diabetes, of which more than a quarter are over the age of 65. It’s believed the significant rate of diabetes is due to an epidemic of obesity paired with chronic elevated glucose levels. 

Diabetes can lead to serious health complications including inflammation, heart attacks, diabetic retinopathy, kidney disease and stroke. It’s believed that 2.8 percent of the U.S. adult population, or 7 million Americans have undiagnosed diabetes. 

The highest rate of undiagnosed cases among Mexican Americans at a rate of 3.3 percent, three times the national average. This is four times the non-Hispanic white American rate of 0.86 percent and 2.59 percent among Asian Americans. 

In contrast, the high rate of diabetes in the U.S., may be due to improved testing and diagnosis among the U.S. population. 

"Traditional methods seem to have captured the large majority of adults with undiagnosed diabetes,” said Fang. “The populations with undiagnosed diabetes may be more difficult to reach. Screening interventions targeting these groups may be needed."