Overview

Macrocytic anemia is a type of anemia that causes unusually large red blood cells. Red blood cells larger than 100 fL are considered macrocytic. Like other types of anemia, macrocytic anemia means that the red blood cells also have low hemoglobin.1

Macrocytic anemia is not a single disease, but a symptom of several medical conditions and nutritional problems.1

Types

Macrocytic anemias are generally classified into megaloblastic or nonmegaloblastic anemia.2

• Megaloblastic anemia is caused by deficiency or impaired utilization of vitamin B12 and/or folate
• Nonmegaloblastic macrocytic anemia is caused by various diseases such as myelodysplastic syndrome (MDS), liver dysfunction, alcoholism, hypothyroidism, certain drugs, and by less commonly inherited disorders of DNA synthesis.2

Symptoms

Anemia develops gradually, so a person may not notice any symptoms until it is severe. When symptoms appear, they may include:1

• weakness
• paleness
• exhaustion
• redness or swelling of the tongue (glossitis)
• diarrhea
• low appetite
• depression
• confusion
• infertility1

Causes and Risk Factors

Megaloblastic anemia is caused by deficiency or impaired utilization of vitamin B12 and/or folate, whereas nonmegaloblastic macrocytic anemia is caused by various diseases such as myelodysplastic syndrome (MDS), liver dysfunction, alcoholism, hypothyroidism, certain drugs, and by less commonly inherited disorders of DNAsynthesis.2