Frequently Asked Questions

Below are some of the questions which are often asked in relation to Vitamin B12 in general and Active-B12 in particular.


What is Active-B12?

Active-B12 is one of the two forms of Vitamin B12 in the blood.

What is Holotranscobalamin?

Holotranscobalamin and Active-B12 are the same.

Why is an Active-B12 test different from the usual Vitamin B12 test?

The usual Vitamin B12 test (also known as Total Vitamin B12 or also as Serum B12) measures all of the Vitamin B12 present in the blood. However, B12 in the circulation is actually composed of 2 types of B12 – Holotranscobalamin (Active-B12) and Holohaptocorrin. Only Active-B12 can be taken up from the blood by the cells of the body to be used in vital cellular processes including DNA synthesis. Holohaptocorrin has no known biological function.

This means that the Total B12 test can give a misleading picture of a patient’s Vitamin B12 status.

I am taking B12 supplements or injections – can my Active-B12 be measured?

The Active-B12 level would be expected to be high if you are receiving B12 supplements. B12 supplementation would have to be suspended before the Active-B12 result could be used to aid a clinical diagnosis. DO NOT STOP B12 SUPPLEMENTATION UNLESS ON THE SPECIFIC INSTRUCTIONS OF YOUR DOCTOR

Can the Active-B12 test be used in the investigation of pernicious anaemia?

Yes. The design of Total Vitamin B12 assays means that the majority of these tests cannot be used in the presence of pernicious anaemia, however, the Active-B12 assay does not suffer from this design flaw and can be accurately used in the assessment of PA.

Where can I have my Active-B12 levels tested?

Many labs around the world now offer Active-B12 testing. Your doctor will be able to advise on availability in your area.