Hemoglobin A1C Levels in Diagnosed and Undiagnosed Black, Hispanic, and White Persons with Diabetes: Results from NHANES 1999-2000

Document Type


Publication Date

Fall 2005

Publication Title

Ethnicity and Disease


Purpose: Although the prevalence of diabetes among various racial/ethnic groups has been well studied, little is known about the racial/ ethnic differences in Hemoglobin A1c (HbA1c) in diagnosed and undiagnosed diabetes. HbA1c correlates with morbidity and mortality in diabetes. Knowledge of the racial/ethnic differences in HbA1c would impact screening and intervention in primary care settings. This study describes racial/ethnic differences in HbA1c among US Black, Hispanic, and White diagnosed and undiagnosed persons with diabetes.

Methods: This study included participants in the 1999-2000 National Health and Nutrition Examination Survey who were > or =20 years old with a HbA1c measurement. The association between HbA1c and race in diagnosed and undiagnosed persons with diabetes (with body mass index [BMI] and age as covariates) was determined. The distribution of HbA1c and mean HbA1c in diagnosed and undiagnosed diabetes and the rates of diagnosed and undiagnosed diabetes with their corresponding HbA1c levels are described by race/ethnicity.

Results: Estimated diabetes prevalence in US persons > or =20 years is 8.2%, with 2.3% having undiagnosed diabetes. Whites with diabetes had lower mean HbA1c levels (7.6%, standard error [SEI 0.2) than Blacks (8.1%, SE 0.3) or Hispanics (8.2%, SE .3). Whites with diagnosed diabetes were less likely to have HbA1c> or =11% (1.7%) than Blacks (11.1%) or Hispanics (10.4%). Hispanics with undiagnosed diabetes were more likely to have HbA1c-7% (60.5%) than Blacks (39.3%) or Whites (37.8%).

Conclusions: Significant numbers of persons with diabetes are undiagnosed. There are significant racial/ethnic differences in HbA1c levels, which are significantly higher in Blacks and Hispanics. Comprehensive risk-based screening and intervention for diabetes is needed in order to address racial and ethnic disparities, especially in minorities.