HealthDay News — The prevalence of diabetes in the United States has increased substantially during the past two decades, but a lower percentage type 2 diabetes cases are going undiagnosed, according to researchers.

In an analysis of data from the National Health and Nutrition Examination Survey (NHANES), only 11% of the national burden of diabetes cases were attributable to undiagnosed cases from 1999 to 2010 versus 16% from 1988 to 1994, Elizabeth Selvin, PhD, MPH, of the Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues reported in Annals of Internal Medicine.

However, the prevalence of total confirmed diabetes increased, from 6.2% to 9.9% during the same study periods, the researchers found. The prevalence of prediabetes also increased from 5.8% to 12.4%.

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In 2010, about 21 million adults had confirmed diabetes as defined by hemoglobin A1C levels of 6.5% and up.

“Despite considerable increases in total diabetes cases over the past two decades, trends in undiagnosed diabetes have remained fairly stable,” Selvin and colleagues wrote, adding this “probably reflects improvements in screening and diagnosis.”

Overall, glycemic control improved among those with diabetes. Total diabetes prevalence was greater and glycemic control was poorer among non-Hispanic blacks and Mexican-Americans compared with non-Hispanic whites.

In an accompanying editorial, Roeland Middelbeek, MD, and Martin Abrahamson, MD, of Joslin Diabetes Center in Boston, attribute the rising prevalence of diabetes and prediabetes to the similar increases in U.S. obesity rates.

“The decrease in percentage of persons with undiagnosed diabetes suggested an increased awareness of the problem and easier methods of diagnosing diabetes,” Middelbeek and Abrahamson wrote, attributing this shift to the recent decision to use HbA1c levels of 6.5% or greater to diagnose the disease.

“However, the use of HbA1c level as a single diagnostic criterion may not diagnose as many patients with diabetes or prediabetes as the fasting plasma glucose level,” they cautioned. “Furthermore, we need to be aware that, by definition, the diagnosis of diabetes or prediabetes should be made if the biochemical findings are confirmed on a second sample.”


  1. Selvin E et al. Ann Intern Med. 2014;160(8):517-525.
  2. Middlebeek RJW, Abrahamson MJ. Ann Intern Med. 2014; 160: 572-573.