Vitamin B12 (active)
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.
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.
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.
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)
Please click here for the link to HCy.
This test is UKAS accredited
Record last updated
August 29, 2025
Sample Container
5ml SST Vacutainers (Gold / Yellow top)
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Test Results
Yes, we have a Pathology User Guide
Yes. Please email your request to Imperial.nwlpcustomerservice@nhs.net
Results are communicated to clinical staff and are normally not communicated direct to patients either on telephone requests or in written report. If you need to contact us please click here to view the contact details page
Please contact the Customer Service Team Monday to Friday from 8:30am – 6:00pm on 0203 313 5353. Alternatively, see the Pathology User Guide for how to contact the relevant department. If advice is not urgent you can also email your query to Imperial.nwlpcustomerservice@nhs.net
Additional tests may be added by discussion with the relevant laboratory. The time limit for adding additional tests to a sample already received in the laboratory will depend on the type of sample and the department it was sent to.
Information on the repertoire of tests performed by pathology, including reference ranges, turnaround times and specimen requirements, can be found in the test directory.
Phlebotomy services are not managed by NWLP. For further information please see:
Imperial College Healthcare Trust Phlebotomy services
Chelsea and Westminster Hospital NHS Foundation Trust Phlebotomy services
NWLP operates UKAS accredited medical laboratories as per the references below. The current scope of accreditation for all NWLP’s laboratories can be found on the UKAS website.
UKAS accredited medical laboratory/medical diagnostic service:
- Clinical Biochemistry No. 8673
- Haematology and Blood Transfusion No. 8674
- Infection & Immunity Sciences (Including Immunology, Virology, Microbiology and Histocompatibility and Immunogenetics ) No. 8659
- Cellular Pathology (Including Histopathology, Cytology and Molecular Pathology) No. 9615
If you require copies of our certificate of accreditation and associated documentation please contact Imperial.nwlpcustomerservice@nhs.net.
UKAS requires the laboratories to be accredited for a particular repertoire/scope (ISO15189), any changes or additions to repertoire require assessment by UKAS (extension to scope).
The BD Hospital Tube Guide, BD GP Tube Guide and BD Paediatric Tube Guide provide visual references to the correct tube types and collection instructions.
Home testing
INSTRUCTION SHEET FOR BLOOD SAMPLE COLLECTION
We also have two instruction videos available (one with subtitles and one without) – please click on the links to view the videos on Google.
Our accreditations
Upholding excellence in diagnostic standards
Our laboratories are accredited by the UK Accreditation Service (UKAS) against the international standard ISO15189:2022. UKAS is the accreditation body for the UK that assesses medical laboratories.
Find out more about our accreditations on the UKAS website.
UKAS website