G6PD deficiency (G6PD-D) variants are associated with lower hemoglobin A1c (HbA1c) concentrations, raising concerns about the diagnostic efficacy of HbA1c for abnormal glucose tolerance (Abnl-GT) in Africans, in whom risk of G6PD-D and Abnl-GT is high. This evidence concerns the gene G6PD and G6PD deficiency.