Question

what is a major cause of macrocytosis?

Explanation:

Macrocytosis (large red blood cells) is often caused by a deficiency in vitamin B12 or folate. These nutrients are essential for DNA synthesis in red blood cell production; their deficiency leads to abnormal, larger red blood cells. Alcoholism, liver disease, or certain medications can also cause it, but B12/folate deficiency is a major cause.

Answer:

A major cause of macrocytosis is a deficiency of vitamin B12 or folate (folic acid), which disrupts normal red blood cell DNA synthesis and leads to the production of abnormally large red blood cells. Other causes can include alcoholism, liver disease, or certain medications, but vitamin B12/folate deficiency is a primary and common cause.