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Vitamin B12 (active)

Category Biochemistry
Test background

Vitamin B12 is essential for DNA synthesis and fatty acid metabolism. Vitamin B12 deficiency can cause megaloblastic anaemia and potentially irreversible neuropathy and neuropsychiatric changes.

Vitamin B12 (cobalamin) exists in two bound forms. Approximately 80% is bound to haptocorrin and 20 % is bound to transcobalamin. The Active B12 test provided only measures holotranscobalamin, the fraction that is available to cells.

Clinical Indications

Active B12 testing should be offered in all patients (including during pregnancy) who have at least 1 common symptom or sign and at least 1 common risk factor for the condition unless the patient is suspected of recreational nitrous oxide use. (NICE NG239)

If NO use is suspected, please check plasma homocysteine as a functional marker of vitamin B12 status. Please see HCy link in the Notes section below. Please note for GP requests, patient must be bled at an NWLP hospital site.

Reference range

25 – 165 pmol/L

<25 pmol/L        confirms vitamin B12 deficiency

25-70 pmol/L     possible vitamin B12 deficiency (indeterminate result)

>70 pmol/L        vitamin B12 deficiency is unlikely

 

Reference range is from the supplier’s information. Interpretative guidance from NICE NG239.

Sample & container required SST (gold top)
Sample volume 0.5 mL
Transport storage If referring from another laboratory, please send frozen
Turnaround time 1 day
Notes

Recent large cohort studies (based on samples representative of the UK population) suggest that people of Black ethnicity may have a higher reference range than people of White/Asian family backgrounds. People of black ethnicity may need treatment at lower concentrations than the cut-offs provided. This will need to be taken into account together with symptoms, signs and risk factors when interpreting test results. (NICE NG239 1.3.13)

This test is new (launched 28th November 2024) so is not accredited. An application will be made to be assessed for accreditation.

Please click here for the link to HCy.