I have severe M.E. along with a few other things, but was diagnosed with B12 deficiency in 2007. Was given loading doses and one more shot after 3 months, then told it was a 'one off' that my b12 level was 76. Nearly a year later my new GP tested my B12 again and my levels were around 160. So went on loading doses again and then shots every three months. My B12 specialist trialled me on B12 shots every week for 6 months but it made no difference to my overall health sadly My gp has agreed to give me a shot every month instead of every three months now but I wonder if there are any other supplements I should be taking, I was low in vit d so take 2000iu of that, my iron wasn't particularly low, and my red cell folate was tested ages ago which appeared normal too? I've also somehow missed 5 months of any shots as the nurses forgot (and so did I.. don't ask how..) but my GP says I don't need loading doses again as my levels would still be high, is this true? I've had terrible chest pains, shortness of breath and dizziness severe again so I'm wondering if it's cos I've not had my B12 (just had it today thankfully..) and of course my exhaustion is severe, I am 99% bedbound apart from when I need to try and get to the bathroom... any help would be MUCH appreciated.
I have also had a couple of tests for PA but no antibodies showed, and we've never actually got to the bottom of why I'm B12 deficient...? Coeliac blood test was negative although I know that isn't accurate and my coeliac biopsy was normal years ago too.
Apologies for the long essay, I hope it's made some sense lol.
Your levels and symptoms indicate that you are B12 deficient (most likely PA but there are other causes), so it's odd that you noticed no difference with B12 shots every week for 6 months, I find that truly baffling (it could be you have very high levels of homocysteine). What i'd do for now is take a daily supplement of folic acid alongside your monthly injections. Without sufficient folate levels, you cannot transform the hydroxocobalamin given by your GP, into methylcobalamin (pure transportive form of B12). Do you have any other symptoms? Numbness/tingling anywhere? Clumsiness? If so, these are the first signs of nerve damage and you NEED the loading doses until these symptoms disappear and then continue with your monthly injections. It's good that your GP put you on monthly injections, as three monthly are not enough for the vast majority of patients with B12 deficiency.
Your B12 levels will not stay high, if you cannot absorb B12, they will only go down, B12 injections are a life-long regime unless the deficiency is diet related. In regards to the PA antibody test, it is highly unreliable (~30%) and so you could have PA but test false for it 2/3 times, this is not a sound diagnostic test for PA.
Best Wishes,
Ken.
(I am not a doctor, your GP is the best person to advise you.)
People with PA have a lack of intrinsic factor which stops the absorbtion of B12 in the gut, hence the injections.
However reduced gut absorbtion can also be caused by gut damage ( after surgery for example), poor diet or certain types of gut bacterial problems.
I would recommend that you have a look at the PAS (Pernicious Anaemia Society) website though. There are lots of people with either PA or B12 defficiencies alongside other health problems. ME being one of them.
We also have problems with our B12 results going up and down and being treated as "normal" even though we still have ongoing symptoms. Soooo, I would suggest you get your GP to re-test the B12 levels before a decision is made as to how much treatment you need and at what frequency. If levels are still significantly low then it may be possible that you need more frequent doses.
There are a lot of technical aspects to PA which I'm not expert enough to precis on here...best to read further for yourself.
I found this paper that seems to suggest that even if you have IF, your bile acid could inhibits the binding B12&IF (if I understood correctly). I've not seen anyone mentioned this so I thought I'd add it here in case you are curious what causes B12 deficiency.
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My gp has agreed to give me a shot every month instead of every three months now but I wonder if there are any other supplements I should be taking, I was low in vit d so take 2000iu of that, my iron wasn't particularly low, and my red cell folate was tested ages ago which appeared normal too? I've also somehow missed 5 months of any shots as the nurses forgot (and so did I.. don't ask how..) but my GP says I don't need loading doses again as my levels would still be high, is this true? I've had terrible chest pains, shortness of breath and dizziness severe again so I'm wondering if it's cos I've not had my B12 (just had it today thankfully..) and of course my exhaustion is severe, I am 99% bedbound apart from when I need to try and get to the bathroom... any help would be MUCH appreciated. 
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