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Causes of low B12 level – (see algorithm below for treatment options)
NB The Schilling test is no longer available.
Indications for measuring B12 level
There is no need to monitor serum B12 levels in patients receiving 3 monthly parenteral vitamin B12 treatment.
If the below indications are present then request B12 levels.
Haematological manifestations can present in the absence of neurological problems and vice versa.
If the patient has non-specific symptoms, consider waiting and retest at a later date if considered appropriate. The ‘Fatigue/Tired All The Time (TATT) pathway on G-care should be followed for patients in which fatigue is the main presenting symptom. The finding of modestly reduced levels in patients with non-specific symptoms is usually of dubious significance.
Secondary tests for B12 deficiency (Homocysteine, MethylMalanoic Acid and Holotranscobalamin) need careful interpretation and are not routinely available locally. MethylMalanoic Acid levels can be accessed as a ‘send away’ test via the Biochemistry laboratory if a good clinical case for the investigation can be made (e.g. a patient with a strong clinical suspicion of B12 deficiency with a borderline /normal B12 level in whom a trial of B12 replacement is not thought appropriate – this should be an unusual occurrence).