From the Guidelines
Hemoglobin A1c (HbA1c) values should be interpreted with caution in patients with anemia as they may be falsely altered, and alternative methods of glucose monitoring should be considered. In patients with anemia, HbA1c results may not accurately reflect average blood glucose levels due to alterations in red blood cell turnover.
- In iron deficiency anemia, HbA1c tends to be falsely elevated 1,
- while in hemolytic anemia or conditions with increased red blood cell turnover, HbA1c may be falsely decreased 1. The reason for these inaccuracies is that HbA1c measures the percentage of hemoglobin that has glucose attached to it, and its accuracy depends on normal red blood cell lifespan. When red blood cell production or lifespan is altered in anemia, the time available for glycation changes, affecting the HbA1c result 1. Clinicians should first treat the underlying anemia before relying on HbA1c for diabetes management decisions, and should consider the specific type and severity of anemia when interpreting results. A complete blood count should be performed alongside HbA1c testing in patients with suspected anemia to help with proper interpretation. Alternative methods of glucose monitoring, such as fructosamine testing, glycated albumin, or more frequent self-monitoring of blood glucose levels, may be necessary to accurately assess glycemic control in patients with anemia 1.
From the Research
Hemoglobin A1c in Anemia
- Hemoglobin A1c (HbA1c) is affected by various clinical conditions, including anemia 2
- Anemia, particularly iron deficiency anemia (IDA), can increase HbA1c levels, and correction of anemia can lead to a decrease in HbA1c levels 2, 3
- The relationship between IDA and HbA1c is complex, and current evidence is inconsistent, with some studies suggesting that IDA may lead to inaccurate HbA1c values 3
Diagnosis and Treatment of Anemia
- Anemia is a common condition, occurring in up to 25% of the US population, and can be classified based on mean corpuscular volume 4
- Iron deficiency anemia is the most common microcytic anemia and can be managed with iron therapy, including oral and parenteral iron 4
- Other types of anemia, such as normocytic and macrocytic anemia, have different causes and treatments, including vitamin B12 and folate deficiency, and require proper diagnosis and management 4
Glycemic Control and Anemia
- Anemia can affect glycemic control in patients with diabetes, and HbA1c may not always be a reliable measure of glycemic control in these patients 5
- Alternative markers, such as fructosamine and glycated albumin, may provide additional information or be more reliable in certain situations, such as in patients with anemia or those receiving peritoneal dialysis 5, 6
- Continuous glucose monitoring (CGM) can also be used to assess glycemic control and provide more accurate information than HbA1c alone 5