Haematology-Oncology · Pathway 2

Vitamin B12 Deficiency

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Key points

Vitamin B12 is mainly used in the body for red blood cell development and also maintenance of the nervous system.
pernicious anaemia
post gastrectomy
disorders of terminal ileum (site of absorption): Crohn's, blind-loop etc
metformin (rare)
KEY TRAP — treat the B12 FIRST: folic acid must not be given alone in undiagnosed megaloblastic anaemia or known B12 deficiency, because it may precipitate or worsen subacute combined degeneration of the cord. If both are deficient, or treatment cannot wait for assay results, give B12 and folate together. Features of vitamin B12 deficiency