Megaloblastic Anemias: Nutritional and Other Causes

Med Clin North Am. 2017 Mar;101(2):297-317. doi: 10.1016/j.mcna.2016.09.013. Epub 2016 Dec 14.


Vitamin B12 and folate deficiencies are major causes of megaloblastic anemia. Causes of B12 deficiency include pernicious anemia, gastric surgery, intestinal disorders, dietary deficiency, and inherited disorders of B12 transport or absorption. The prevalence of folate deficiency has decreased because of folate fortification, but deficiency still occurs from malabsorption and increased demand. Other causes include drugs and inborn metabolic errors. Clinical features of megaloblastic anemia include anemia, cytopenias, jaundice, and megaloblastic marrow morphology. Neurologic symptoms occur in B12 deficiency, but not in folate deficiency. Management includes identifying any deficiency, establishing its cause, and replenishing B12 or folate parenterally or orally.

Keywords: Anemia; Folate; Homocysteine; Megaloblastic; Methylmalonic acid; Pernicious anemia; Transcobalamin; Vitamin B(12).

Publication types

  • Review

MeSH terms

  • Anemia, Megaloblastic / diagnosis
  • Anemia, Megaloblastic / etiology*
  • Anemia, Megaloblastic / physiopathology*
  • Comorbidity
  • Folic Acid Deficiency / complications
  • Folic Acid Deficiency / drug therapy
  • Humans
  • Metabolic Diseases / complications
  • Nutrition Disorders / complications
  • Prevalence
  • Vitamin B 12 Deficiency / complications
  • Vitamin B 12 Deficiency / drug therapy