Effects of Iron Deficiency Anemia on Hemoglobin A1c in Type 1 Diabetes Mellitus

Background: The relationship between hemoglobin A1c (HbA1c) and iron status in type 1 diabetes mellitus (DM) has not been adequately studied. In this prospective investigation, we aimed to determine the effect of iron deficiency on HbA1c in diabetic patients who also had insufficient iron stores.

Methods: Thirty-seven patients with type 1 DM were included in the study. Eleven of them were also iron deficient (ID) and the remaining 26 were iron-sufficient (IS). Two non-diabetic control groups were selected for the ID and IS groups. All patients with ID were treated with iron at 6 mg/kg per day for 3 months. Glycemia in diabetic patients was monitored at home before breakfast and supper by a glycometer. Hemoglobin A1c was measured in all subjects at the beginning and the end of the study.

Results: Patients with ID DM had higher levels of HbA1c than those in the control group (P < 0.001). There were no significant differences in the weekly average glucose concentration of the patients with ID DM before and after iron supplementation. In contrast, HbA1c decreased from a mean of 10.1 +/- 2.7% to a mean of 8.2 +/- 3.1% (P < 0.05). Additionally, HbA1c in ID non-diabetic patients decreased from a mean of 7.6 +/- 2.6% to 6.2 +/- 1.4% after iron therapy (P < 0.05).

Conclusions: We conclude that among type 1 DM patients with similar level of glycemia, iron deficiency anemia is associated with higher concentrations of HbA1c. In addition, iron replacement therapy leads to a drop in HbA1c in both diabetic and non-diabetic patients. The iron status of the patient must be considered during the interpretation of HbA1c concentrations in type 1 DM.