indications to measure vitamin B12 levels

Last edited 05/2022 and last reviewed 05/2022

Indications for measuring serum vitamin B12 level (1):

  • Haematological (in increasing order of severity):
    • isolated red cell macrocytosis
    • macrocytic anaemia (esp. if MCV >110 fl)
    • pancytopenia (esp. if MCV >120 fl)
  • Neurological or psychiatric:
    • peripheral neuropathy
    • cognitive change e.g. dementia
    • optic neuritis
  • Gastrointestinal:
    • investigation of possible malabsorptive process
  • Other (rare):
    • angular cheilosis
    • sore beefy red tongue

Haematological complications of vitamin B12 deficiency can present in the absence of neurological problems and vice versa.

Testing should be restricted to those with suspected vitamin B12 deficiency and should not be used as a screening test (2).