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Pernicious Anaemia Society
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What blood test should I ask for

Hi guys, I am starting to think I may have a functional B12 deficiency, I have an appointment with my doctor on Monday and I need to try and convince her of this. Are there any blood test to show a functional def, is there any medical papers that explain what a functional deficiency is? I'm currently SI every two weeks but still im getting symptoms.

Thanks guys

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Hi Pixielula, I didn't get diagnosed with functional B12 deficiency until it became clear after my 2nd 3-monthly injection that I was going further downhill. 6 weeks after this injection, I was tested for MMA levels, which were high: this should not be the case after injections. Homocysteine levels apparently can also be checked for this, but I did not have that done.

I really think that my Dr talking to a haematologist, after getting a letter from me, may have been what goaded her into action. She booked me straight in for reloading injections, before getting results, so I guess the haematologist said this was urgent. Currently on 2 injections a week and have been for a while. Improvement very slow and erratic, still hopeful. You need a Dr that you can trust to do the right thing by you, and admit when something is beyond them alone. Best of luck. Let us know how it goes.

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MMA and homocysteine should be raised if you have a functional B12 deficiency - they are looking at waste products that will build up if you aren't getting enough B12 at the cell level.

Not much out there on functional B12 deficiency but there is this paper from a few years ago which was arguing that high levels of B12 should be investigated and talks about functional deficiency being the symptoms of B12 in the presence of high B12 levels - its basically arguing that high levels of B12 can be early indicators of other conditions so if B12 levels are high it should be investigated


few other articles





Thank you for the links gambit but I don't really understand the complexities of what I'm reading. My only thoughts are my last two serum b12 bloods are very high over 1500 (I think my lab only measures up to 1500) but Within a couple of days of injecting the fatigue and dizziness starts to return and I get pain in my thighs calves and arm muscles. I'm desperately trying to understand why this is. I'm totally frustrated being told my symptoms can't be b12 related, when I know they are. My doctor would be happy to diagnose me with ME and FM, so I'm trying to find anything that would help her understand the b12 connection and get more frequent injections that 12 weekly. I suppose in order to do that I need to put a comprehensive aregument together. An I haven't got a clue!!


I know what you mean. If I don't get a jab every 10 days then I start going downhill fast. I get totally knackered after just a little effort and the pain across the back of my neck and shoulders gets quite bad.

My B12 is sky-high, my MMA and hCys are both low, so doc is sure it can't be B12. What persuaded him was my symptom and treatment diary. Fatigue is the best indicator so I made a graph that shows my fatigue levels (scored 0 to 10) and when I had an injection and used a patch (gave them up when it became clear they didn't work. Here's what it looked like -


I went gluten-free for three weeks as it had been suggested that my symptoms might have been due to that. After 12 days without a jab I couldn't even cook the evening meal and we had to get a delivery. Now I'm back on the bread - yum!

I'm certain that there's something else that B12 does that is causing the problem. I've no idea what though. I do have ideas on how it could be researched, but it would cost a bit of cash. If anybody happens to have a spare £3 million I'd love to give it a go.


So if I get my Gp to do MMS and homocysteine, does it matter that I'm injecting? Will that alter the test results ?


If you want to find out if you have a functional deficiency (loads and loads of B12 in the blood, but none where it's supposed to be) then you'll want loads and loads of B12 in the blood.

Otherwise, if you test with really low B12 levels all you'll be showing is that you've got really low levels of B12 in the blood.

This page includes a section on functional deficiency (under 'Differential Diagnosis) patient.info/doctor/pernici... with a link to a paper - ncbi.nlm.nih.gov/pubmed/191...

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one of the key elements of functional deficiency seems to be that there appears to be a level above which sufficient B12 does actually get through to cell level - so when you are feeling okay that's when enough is getting through and homocysteine and MMA will probably not be elevated.

This would suggest that what you need to do is to find that point tipping point and stay below it for a while - serum B12 would be high but you would have given yourself enough time being deficient at the cell level for homocysteine and MMA to start building up. I would imagine that this point is not going to be an easy one to find though.

However, at the end of the day it is also possible that there is more than just B12 going on and you need to be open to that possibility as much as medics need to be open to the possibility that treatment with B12 per the standard regime may not actually be an effective treatment for some patients.


And that I suppose is the crux of the matter, I'm assuming that this is all b12 related as all problems go away directly after a shot. I can have debilitating fatigue I was taking paracetamol and diclofenac last week for the pain in my legs and the day after my injection no fatigue no pain, all of which my doctor sees as anecdotal and not proof. Surely if I had ME I would still have the fatigue after the shot surely if I had FM the pain would still be there? The anecdotal evidence is all I have to go on. Last Wednesday I did a 14 hour day at work the following morning I could hardly walk due to the pain in my legs and was so dizzy I fell into my wardrobe.


Not sure I'd entirely agree that the evidence is totally anecdotal. What makes evidence anecdotal is the lack of a scientific methodology in its collection. Keeping a good diary of what happens with times etc, showing that the improvement is repeatedly related to maintenance shots and if possible getting a third party - friend/relative to confirm that they have seen the effects would be a good starting point. Also being clear that this is the only factor is changing would be good.

On the other hand, B12 has been shown to help patients with MS - not so sure about FM.

I can't guarantee that GP will listen but ...

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I was taking paracetamol and diclofenac last week for the pain in my legs

What sort of pain? Neuropathic pain is infamous for not responding to normal pain killers. but gabapentin, and others, do a good job of improving it.


I don't know if it was neuropathic, just very painful muscles, painful to walk and go up and down stairs painful to touch felt like I had cycled 50 miles, uphill against gale force winds..... so in order to have raised levels of MMA and homocysteine how long would I need to go without any b12 do you think?


there appears to be a level above which sufficient B12 does actually get through to cell level - so when you are feeling okay that's when enough is getting through and homocysteine and MMA will probably not be elevated.

I know you've posted this before. But it just clicked with me that this makes a lot of sense.

Back in January I tried going for almost three weeks without a jab before having MMA and hCys tests. But that may not have been long enough for levels to rise.

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the articles are ones that you could show to your doctor to show them that functional deficiency isn't just a term that you have made up but a real phenomenon.

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Oh I will get my check book :-)


So I'm going to tell her that I am taking huge amounts of high dose sublinguals, not that I'm SI every two weeks? I don't want to freak hee her out completely


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