PTD - 45

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Test Directory -  Vitamin B12



Clinical Indications

Investigation of suspected vitamin B12 deficiency. Follow-up of megaloblastic anaemia, macrocytosis or nutritional anaemias. Detection of vitamin B12 deficiency found in pernicious anaemia, folic acid deficiency. In other situations, low levels of vitamin B12 does not necessarily indicate significant clinical deficiency.

Request Form


Combined Pathology Blood form (Yellow/Black or Blue for GP's)


On request

Specific Criteria

Needs to be on initial request form and cannot be added on later.

Turnaround Time

Same day




1 ml


Yellow top (SST)

For paediatric samples a Paediatric Lithium Heparin (Orange top) may be used.


No specific collection conditions.

Causes for Rejection

Unlabelled or incorrectly labelled or insufficient patient identifiers sample. Not meeting specific criteria for analysis. Delay in sample reaching laboratory.  Insufficient sample volume.



Samples should not be taken from patients receiving therapy with high Biotin doses (>5mg/day) until at least 8 hours following last biotin administration.

Reference Range

Adults: 150 - 900 ng/L (units changed on 30.12.2011 from pmol/L to ng/L)

Unit Conversion

To convert from pmol/L to ng/L multiply by 1.355


Low B12 results occur in Pernicious Anaemia, achlorhydria, vegans, poor diet or malabsorption and up to 10% of elderly. Intrinsic factor positive patients should receive life-long parental B12 therapy. The specificity of a low B12 of <180 ng/L for tissue deficiency is only 50%. If dietary deficiency is suspected a trial of oral therapy with clinical review may be appropriate. Please contact your Haematologist for further advice if required.



Version 1.1 / February 2017