Decreased HbA_1c Levels Due to Sulfonamide-Induced Hemolysis in Two IDDM Patients

Regular measurement of HbA_1c (percentage) is an essential component of modern diabetes care. Factors that affect the life span of erythrocytes will also influence HbA_1c results. In this study, we describe two patients with IDDM, whose regularly determined HbA_1c values were considerably decreased with the concomitant use of two related sulfonamide drugs, sulfasalazine and dapsone. The fall in HbA_1c results is explained by increased erythrocytopoiesis as a product of drug-induced hemolysis. Fructosamine concentrations are not affected by hemolysis and reflected glycemic control better. We conclude that under conditions of persistent (subclinical) hemolysis, as occurs during the use of sulfonamides, HbA_1c is not a reliable indicator of glycemic control.