Pernicious Anaemia Society

B12 and Active B12

I've just recently joined the Thyroid community -- I have Hashimoto's and Coeliac -- and was asked to post this query here... Checking back through my B12 tests I can see that I am skipping along the lower 10-20% of the range for B12, and the top 10-20% range for Active B12. I'm in Sydney and testing for Active B12 is standard if B12 is low; see What is the situation in UK, Canada etc and how are the tests different, and how reliable?

2 Replies

active B12 has one advantage over serum - that it only looks at the forms of B12 that are bound to proteins that allow them to pass into cells.

However, like serum B12 it is still a measure of what is happening in the blood and not what is happening at the cell level - there are different indirect tests that can help with that namely MMA and homocysteine

Blue_Bee - your results are still within the normal ranges on both even if towards top on one and bottom on the other. 5% of people who are off the bottom of the range will actually be okay.

overlap of symptoms with thyroid problems is going to make evaluating symptoms difficult - so MMA might help


Wow, this is really helpful. Thank you! Fx


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