Macrocytosis can occur when there is increased RBC production secondary to peripheral blood cell destruction (i.e., hemolysis) or loss (i.e., hemorrhage), leading to a reticulocytosis. Reticulocytes are incompletely processed RBCs and, therefore, are slightly larger than the average RBC.

How does enlarged red blood cells affect the body?

Red blood cells larger than 100 fL are considered macrocytic. When the cells grow too large, there are fewer of them than there needs to be and they carry less hemoglobin. This means the blood is not as oxygen-rich as it should be. Low blood oxygen can cause a range of symptoms and health problems.

How serious is macrocytosis?

However, macrocytic anemias can cause long-term complications if left untreated. These complications can include permanent damage to your nervous system. Extreme vitamin B-12 deficiencies may cause long-term neurologic complications. They include peripheral neuropathy and dementia.