What Is Macrocytic Anemia?

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The red blood cells are the portion of the blood that carries the hemoglobin protein. Because hemoglobin is responsible for binding oxygen and transporting it around the body, a deficiency in red blood cells, also known as anemia, can have serious consequences for the body. People suffering from anemia often feel tired as a result of insufficient oxygen transport and typically appear pale. Different anemias can be distinguished in part by the appearance of the red blood cells when viewed under a microscope.


Macrocytic anemia is a condition in which there are insufficient numbers of red blood cells and the red blood cells that are produced are larger than normal. Macrocytic anemia differs from microcytic anemias (small red blood cells) and normocytic anemia (normal-size red blood cells) in this aspect. Macrocytic anemia is also identified by the red blood cells having abnormally low levels of hemoglobin (a protein that is necessary for oxygen transport).

Megaloblastic Anemia

Megaloblastic anemia is one type of macrocytic anemia in which the red blood cells grow too large because of insufficient DNA synthesis in the bone marrow. When DNA synthesis occurs too slowly, fewer red blood cells are formed and the ones that are formed have had more time to grow, leading to them being larger than normal. Megaloblastic anemia is often a result of vitamin deficiency (folate or B12), or can occur as a result of chemotherapy that is toxic to the bone marrow.

Refractory Anemia

Refractory anemia incidence occurs as a result of a disorder involving the bone marrow. The anemia types intrinsically related to bone marrow disease, such as aplastic anemia or myelodysplastic anemia, in which the bone marrow (which is responsible for making red blood cells) is unable to produce them in sufficient quantity. The red blood cells it does make are also abnormal, with large size again being the result. These conditions often can lead to leukemias, which are cancers of the bone marrow and blood cells.

Alcohol and Other Causes

Chronic alcohol abuse is also associated with macrocytic anemia, as it appears that alcohol can be toxic to the bone marrow. Other conditions, such as liver disease and sudden blood loss, can lead to macrocytic anemia, as the bone marrow produces slightly immature red blood cells in response to low quantities of red blood cells in the body. Once again, these immature red blood cells are slightly larger than normal.


Treatment of macrocytic anemia generally has two parts. The first part is to treat the anemia by administering blood products or by giving a blood transfusion. This will help correct the deficient supply of red blood cells. The next step is to identify the cause of the macrocytic anemia (be it a vitamin deficiency, bone marrow problem, or some other cause) and to treat the underlying condition.

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