Vitamin<unk> , also known as cobalamin, cyanocobalamin
Ingested in dietary form
Binds to intrinsic factor, a protein secreted by gastric parietal cells<unk> -intrinsic factor complex then absorbed in the terminal ileum
Stored in liver, takes up to 3 years to deplete hepatic stores after ceasing intake
Causes of<unk> :
Decreased intake (e.g. strict vegan diet)
Competition in gut (e.g. blind loop syndrome, fish tapeworm)
Intrinsic factor<unk> 
Pernicious anemia (associated with atrophic gastritis, IgA<unk> , polyglandular endocrine failure)
Post-gastrectomy
Decreased ileal absorption (e.g. post ileectomy, Crohn's disease)
Pancreatic insufficiency
H. pylori infection
Binds to intrinsic factor, a protein secreted by gastric parietal cells<unk> -intrinsic factor complex then absorbed in the terminal ileum
Stored in liver, takes up to 3 years to deplete hepatic stores after ceasing intake
Decreased intake (e.g. strict vegan diet)
Competition in gut (e.g. blind loop syndrome, fish tapeworm)
Intrinsic factor<unk> 
Pernicious anemia (associated with atrophic gastritis, IgA<unk> , polyglandular endocrine failure)
Post-gastrectomy
Decreased ileal absorption (e.g. post ileectomy, Crohn's disease)
Pancreatic insufficiency
H. pylori infection
Pernicious anemia (associated with atrophic gastritis, IgA<unk> , polyglandular endocrine failure)
Post-gastrectomy
Vitamin B12 deficiency
Hemorrhage
Vitamin B7 deficiency
Hereditary
Vitamin B9 deficiency
Acquired
Vitamin A deficiency
Microangiopathic Hemolytic Anemia 