Decreased HbA1c levels due to sulfonamide-induced hemolysis in two IDDM patients.

Regular measurement of HbA1c (percentage) is an essential component of modern diabetes care. Factors that affect the life span of erythrocytes will also influence HbA1c results. In this study, we describe two patients with IDDM, whose regularly determined HbA1c values were considerably decreased with the concomitant use of two related sulfonamide drugs, sulfasalazine and dapsone. The fall in HbA1c 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, HbA1c is not a reliable indicator of glycemic control.