Pernicious Anaemia Society
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Activated B12 for MTHFR gene mutant

Being a mutant(!), my newly acquired GP believes that I cannot absorb the regular B12 injection so I need to have activated B12. Sadly a loading dose has not been offered to me, just a one off injection. Still feeling dreadful, I am left wondering if there is any difference in the recommendation for activated B12 loading dose and continuance until neuro symptoms decrease?

I was so delighted to find a GP who considered PA, and it's links to MTHFR and Hashimotos. However, now I'm wondering if the GP really knows the PA side of things. He's not one who likes the balance of power to be shifted in favour of the patient, so I have to tread carefully!

Anyone been down this road? If I choose to self inject, what is activated B12 and how do I get it?

I'm getting a bit desperate with my neuro signs unchanged, I so don't want them to be permanent.

4 Replies

activated forms of B12 are the methylated forms - ie methylcobalamin and adenosylcobalamin. Methyl is the one that is used and this is the format that is used for repair of the sheath that insulates nerve cells which is what goes wrong when you don't get enough B12.

Do you know exactly which gene is affected and if you are homozygous or heterozygous (inherited from both or just one parent? - as this will also affect the treatment.

You presumably also have problems converting folate to methylated forms - what is your GP doing about this?

Not entirely convinced personally that MTHFR means you can't process the unmethylated forms - just that you are less efficient and so need higher levels but that really is a personal opinion.

there is a reference to that in this document


You can purchase methylated B12 from and there are also some that cell dried format (not covered by UK prescription only rules) that you then have to mix with saline.


I'm A1298C heterozygous, so not in the worst case scenario category.

I take folinic acid and avoid folic acid.

It's all so very complex!!


It sure is complicated, I am positive for the 667 mutation and take Methylfolate and Methylcobalamin.

This is a very recent development for me and thankfully I'm beginning to see a bit of an improvement.

Is there a difference in Methylfolate and Folinic acid? I am surprised that you are not getting more injections.

What was your B12 level to start off?



I was over 600 but they didn't do MMA and homocysteine


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