From the Guidelines
Iron deficiency anemia can falsely elevate A1c levels, potentially leading to misdiagnosis or overtreatment of diabetes, as it prolongs erythrocyte life span and exposes the cell to glucose for a longer period, as noted in the 2017 study 1. This occurs because iron deficiency extends the lifespan of red blood cells, allowing more time for hemoglobin glycation to occur. The effect is most significant when hemoglobin levels drop below 10 g/dL, with A1c potentially increasing by 0.5-1.5 percentage points. The relationship between iron deficiency anemia and A1c levels is also supported by a 2006 study 1, which found that iron-deficiency anemia is associated with increased HbA1c.
Key Considerations
- Clinicians should consider checking iron studies (ferritin, transferrin saturation) when A1c results don't align with other glycemic measures like fasting glucose or when anemia is suspected.
- After iron repletion therapy (typically oral ferrous sulfate 325mg daily for 3-6 months), A1c levels should be retested as they typically normalize within 3 months of correcting the iron deficiency.
- For diabetes management decisions in patients with known iron deficiency, alternative glycemic markers such as fructosamine, glycated albumin, or continuous glucose monitoring may provide more accurate assessment of glycemic control until the anemia is corrected, as suggested by the 2017 study 1.
Clinical Implications
- It is essential to interpret A1c results in the context of patient characteristics and nonglycemic factors, including iron deficiency anemia, to avoid misdiagnosis or overtreatment of diabetes.
- Clinicians should be aware of the potential impact of iron deficiency anemia on A1c levels and take this into account when making diabetes management decisions.
From the Research
Relation of A1c and Iron Deficiency Anemia
- The relationship between A1c and iron deficiency anemia has been studied in several research papers 2, 3.
- Iron deficiency anemia can affect hemoglobin A1c (HbA1c) levels, and treatment of iron deficiency anemia can decrease HbA1c in anemic patients with type 2 diabetes mellitus (T2DM) 2.
- A study found that iron replacement therapy can improve HbA1c levels in patients with T2DM and iron deficiency anemia, suggesting that iron status should be considered during the interpretation of HbA1c concentrations in diabetes mellitus 2.
- Another study found a positive and significant relationship between Hb A1C and Hb levels before and after treatment, and concluded that there is a negative correlation between Hb A1C and Hb 3.
- The use of intravenous iron has been studied as a treatment for iron deficiency anemia, particularly in patients who are intolerant to oral iron or have severe anemia 4, 5, 6.
- Intravenous iron preparations can facilitate rapid iron repletion and are indicated for the treatment of iron deficiency when oral preparations are ineffective or cannot be used 5.