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"What causes red blood cells to get bigger?"


After a recent routine blood test, my doctor advised me that I have enlarged red blood cells. She presented it as a problem that wasn't too threatening, but I'm still concerned. What deeper problems can cause enlarged red blood cells? What should I investigate?


There are multiple causes of enlarged red blood cells, which is termed macrocytosis, and most of them are easily corrected. Two of the most common causes are deficiencies in vitamin B12 and folic acid, which are frequently associated with anemia, as well. However, there are also other important causes of macrocytosis not associated with vitamin deficiencies.

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Chief among them is pregnancy, however it is likely that you and your doctor are already aware of whether this is a possible cause of your macrocytosis. Other causes of macrocytosis include hypothyroidism, disorders of the bone marrow itself, increased production of immature blood cells, and certain medications, especially chemotherapathy drugs. Alcohol use is also another important factor that can lead to macrocytosis. It can do so both indirectly by leading to nutritional deficiencies, but also directly by inhibiting the production of mature red cells. Most of these conditions are associated with other symptoms such as fatigue as in the case of hypothyroidism, or numbness and tingling in the case of vitamin B12 deficiency. Your primary care physician can check a number of very simple blood tests that will help him or her determine which potential causes are most likely and what the best treatment options are.

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