Causes of enlarged red blood cells, or macrocytosis, include folate deficiency, vitamin B-12 deficiency, liver disease, alcoholism and medication side effects, according to Mayo Clinic. Hematologists usually detect macrocytosis cases on routine blood tests on asymptomatic patients.
Medications that cause macrocytosis include cancer treatments, autoimmune therapies and anticonvulsants, Mayo Clinic states. Another cause is the red bone marrow overproducing red blood cells to compensate for their loss during a period of anemia.
Patients with chronic liver disease experience this condition due to excess red blood cell (RBC) membranes, according to Merck Manuals. As RBC membranes form in the spleen, a person who has undergone a spleenectomy may experience macrocytosis. This condition can occur with and without a folate deficiency in those who drink too much alcohol, but it is more common among those who are folate deficient. The most common cause is a vitamin B-12 deficiency, which arises either due to the patient not eating enough or their body not absorbing it. In some cases, this condition arises because the patient's DNA doesn't synthesize correctly.
As macrocytosis usually becomes apparent in asymptomatic patients undergoing a routine blood test, doctors may perform further tests to identify the cause, according to Mayo Clinic. However, there isn't always an apparent cause, states Merck Manuals.