Association Between Serum Ferritin and Hba1c in Non-Diabetic Patients With Iron Deficiency Anaemia: A Comparative Cross-Sectional Study

Background: Iron deficiency anaemia (IDA) may influence glycated haemoglobin (HbA1c) independently of glycaemia, potentially causing misclassification of non-diabetic individuals. This study assessed the association between serum ferritin and HbA1c in non-diabetic adults with IDA. Materials and Methods: This comparative cross-sectional study included 130 participants aged 18–65 years: 65 patients with confirmed IDA and 65 non-anaemic controls. Participants with diabetes, significant inflammation, haemoglobinopathies, haemolytic anaemia, recent transfusion, pregnancy, liver failure, or renal failure were excluded. Haemoglobin, serum ferritin, HbA1c, fasting blood glucose, postprandial blood glucose, and relevant biochemical parameters were measured. Between-group comparisons and Pearson correlation analyses were performed, with p<0.05 considered statistically significant. Results: Mean serum ferritin (8.42±2.64 versus 29.58±9.59 µg/L) and haemoglobin (4.90±1.09 versus 13.00±2.48 g/dL) were significantly lower in the IDA group than in controls (both p<0.001). Mean HbA1c was significantly higher in the IDA group (5.99±0.22%) than in controls (5.25±0.13%; p<0.001), although fasting and postprandial glucose values remained below diabetic thresholds. Among patients with IDA, 90.8% had HbA1c of 5.7–6.4% and 4.6% had HbA1c ≥6.5%, whereas all controls had HbA1c <5.7%. HbA1c correlated negatively with serum ferritin (r=−0.389, p=0.001) and haemoglobin (r=−0.308, p=0.012) in the IDA group. Conclusion: Severe IDA was associated with higher HbA1c despite non-diabetic glucose values. HbA1c should therefore be interpreted cautiously in iron-deficient patients, and abnormal results should be corroborated using glucose-based testing and reassessed after correction of iron deficiency. These findings highlight the importance of assessing iron status when HbA1c is used for diabetes screening, particularly in populations with a high burden of anaemia.