Table 4.

Common causes of macrocytosis [14]

Megaloblastic macrocytosis (vitamin B12 and/or folate deficiency)	Non-megaloblastic macrocytosis	False elevation mean corpuscular volume (MCV)
1. Atrophic gastritis	1. Alcohol abuse	1. Cold agglutinin
2. Enteral malabsorption	2. Medication side effects	2. Hyperglycemia
3. Human immunodeficiency virus treatment	3. Myelodysplasia	3. Marked leukocytosis
4. Anticonvulsants	4. Hypothyroidism
5. Primary bone marrow disorders	5. Liver disease
6. Nitrous oxide abuse	6. Hemolysis
7. Inherited disorders	7. Hemorrhage
	8. Chronic obstructive pulmonary disease
	9. Splenectomy