Pernicious Anaemia Society
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MTHFR compound heterozygous mutation

That's a mouthful right there!

I have what is known as a compound heterozygous mthfr mutation. Basically this means that I received one faulty copy of two different genes that deal with methylation. In a practical sense, it affects enzyme production that breaks down folate and homocysteine and it's estimated that this mutation combination affects function by 50%.

I had some blood tests done in August 2014, which showed a B12 level of 374, ferritin of 8, and folate of 4.8. Not stellar, but I was still upright.

I was prescribed ferrous fumarate for the ferritin problem but the other two were 'normal' so no action. I decided to supplement 1000mcg methylcobalamin per day and take a B complex too.

My question is what levels of B12 would you expect to see in someone who takes 1000mcg per day? I would imagine that they'd be quite high (1000+?) but my last B12 test showed a level of 750, having stopped the supplements 2-3 weeks beforehand. I can't help the feeling that if I stopped for longer I'd be back in under 500 territory...

I appreciate that this is a 'piece of string' question but I'd be interested to know what you think.

2 Replies

Assuming that you don't have an absorption problem the body is actually really efficient at storing any B12 it doesn't need in the liver - so it wouldn't necessarily build up in serum.


I took 1000mcg of B12 a day for six months after a B12 level of 370 and it went up to about 540 (I don't have the numbers to hand but it was something like that). I have positive anti parietal cell antibodies. I managed to get the nurse to do the test just before my first injection so I could see whether taking the B12 orally had made a difference.


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