The diagnosis of prediabetes and diabetes mellitus is often assigned based on assessment of discrete hemoglobin A1c (HbA1c) levels. Several studies have identified factors that affect HbA1c, including African ancestry,1 chronic kidney disease,2 and iron deficiency anemia.3 Increasing evidence suggests that at a given glucose level, white people have lower HbA1c levels than black people,4 although the effect of sickle cell trait (SCT) on HbA1c levels is not clearly defined. Approximately 10% of the black population has SCT.
Bleyer AJ, Aloi JA. Sickle Cell Trait and Interpretation of Hemoglobin A1c Levels. JAMA. 2017;317(5):481-482. doi:10.1001/jama.2016.20994