Macrocytosis is a medical term used to describe enlarged red blood cells, according to Mayo Clinic. This medical condition usually does not cause any symptoms, but it may be a symptom of an underlying disease or infection.
Macrocytosis is most often found during routine blood tests, according to Mayo Clinic. When seen, doctors may need to run more tests to determine the cause of the patient's red blood cells being larger than normal. A few of the conditions that cause enlarged blood cells include vitamin B-12 deficiency, folate deficiency, alcoholism, hypothyroidism and liver disease. To treat macrocytosis, it is necessary to treat the underlying condition.