Causes of vitamin B12 deficiency

Common causes (related to malabsorption)
Autoimmune gastritis (pernicious anemia)
Celiac disease
Inflammatory bowel disease
Surgical gastrectomy, gastric bypass, ileal resection
Less common causes
Nutritional (strict vegans, breastfed infants of mothers with vitamin B12 deficiency)
Nitrous oxide abuse
Diphyllobothrium latum infection
Pancreatic insufficiency
Drug effect (metformin, proton pump inhibitors)
Inherited disorders affecting intrinsic factor or the cubam receptor
Rare inherited disorder (eg, methylmalonic acidemia, transcobalamin II deficiency)
  • Information from references 4, 5, and 7.