B12 different ranges

[Marymary7]

Please can someone correlate the active B12 with these other ranges. It was taken from a restless legs article in Pernicious Anemia Society article. Trying to help my brother, his latest tests are active B12. Many thanks for any help.

“The 2024 NICE guideline on B12 deficiency recommends diagnosing B12 deficiency at levels below 180 pg/mL, and to do a further test for people with levels between 180-350 pg/mL. Therefore, with an average of 168pg/mL, over half of the participants in this study with restless legs would be considered B12 deficient according to the NICE guideline.”

[Gambit62 Administrator]

In general active B12 is 20% of serum B12 but that is a rule of thumb and can't be applied to a specific individual or a specific test result.

[Marymary7 in reply to Gambit62]

My brothers active B12 was 53.4. His GP is refusing to carry out the MMA test which the Medichecks Doctor advised and is doing nothing.

[Gambit62 Administrator in reply to Marymary7]

MMA often isn't available at GP practices.

[Marymary7 in reply to Gambit62]

I know it’s expensive. Do you know if his levels are worryingly low at 53.4. He has M.S and is severely disabled. I’m concerned the lack of B12 is making him worse.

[Gambit62 Administrator in reply to Marymary7]

I'd refer you back to the lab comments and the range that came with the results when you had them done. Both serum and active B12 have very large ranges so drawing a conclusion about a specific individual is very difficult.

Please note that this forum is not a substitute for professional medical advice.

[Marymary7 in reply to Gambit62]

Sorry, i don’t understand the difference ranges between active B12 and the free. Thanks for your opinion its much appreciated.

Results

[Gambit62 Administrator in reply to Marymary7]

serum b12 measures all B12 in blood. Serum B12 measures only B12 bound to a protein called transcobalamin which enables it to pass into cells. Generally the amount of B12 bound to transcobalamin is 20% but it can vary - which means that the two tests aren't readily translatable.

On the face of it your son has a level of active B12 in his blood that would be adequate for 90% of the population - though that doesn't mean it is necessarily adequate for him.

I notice that folate is marked as low. Symptoms of folate deficiency overlap considerably with B12 deficiency because the two are used together in a lot of processes. MMA is a test of a metabolite from a process that only involves B12 and not both B12 and folate so it is potentially a good marker for distinguishing where B12 specifically is low. Homocysteine is dependent on both folate and B12 so it isn't good for indicating B12 specifically. Both tests are indirect measures of B12 status and can provide a clue as to what is happening in cells.

Serum B12 and Active B12 are both measures of B12 levels in blood and don't give an indication of how B12 is being used by cells. The ranges are also very large because there is a lot of individual variation in what is right for a person - though generally levels are pretty constant - so they are probably best used in identifying an absorption problem by monitoring for a drop over time. What constitutes a drop depends on the accuracy of the test - serum B12 is less precise than active B12 and you would need a drop of more than 20% for the fall to be significant (outside the range of variation from repeating the test several times).

I believe the reason why MMA isn't generally available through GPs is to do with needing to run the test within quite a tight time frame once the sample has been extracted. You may need to ask for a referral to a haematologist to get the test done.

If the reason for folate being low is an absorption problem then that makes it very likely that B12 absorption is also affected.

[Marymary7 in reply to Gambit62]

Many thanks for your detailed reply, much appreciated.