"Function B12 Deficiency" : Hi, My... - Pernicious Anaemi...

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"Function B12 Deficiency"



My English GP received my blood test results from St Thomas' hospital. The active b12 and MMA indicate " functional b12 deficiency at tissue level. "

I actually live in Spain and paid for these tests privately as the active b12 is not available here at all.

I have numerous, and now quite debilitating symptoms including neurological involvement. Probably started around 6 years ago, steadily getting worse until Oct 2014 when all symptoms got a lot worse. My Total Serum the past few years had been within" normal" range at 434. My GP here in spain had actually started me on 2 weekly jabs in Nov due to my worsening symptoms as a sort of trial. I had had one jab prior to the active b12 test which till showed low. I have since had a further 4 jabs with not much change in symptoms. After the last jab I had a bit less fatigue/weakness and achiness for a couple of days only. I do seem to have stopped losing weight though for the first time in 12 months and my appetite is better.

I see my GP for a review anyway next week as the prescription has run out. I will take my lab report with me and try and explain about the active b12 test and MMA.

Does anyone have experience of "Functional b12 deficiency" (the NHS website says it is where the proteins aren't transporting the b12 to the cells) and what treatment should I be hoping for? I'm guessing that I need more frequent injections than every 2 weeks......

Any comments appreciated. Thanks.

18 Replies

You may find these articles of use



Note: second article isn't an argument against B12 supplementation but talks about functional deficiency in general and what may give rise to a functional deficiency when there are high levels of B12 in serum - though the levels you report weren't at the high end of the scale but in the grey range.

Your problem may be genetic - an autoimmune response that according to one of the studies mentioned in the second article may affect 30-40% of the population.

First article is all I have been able to find on treating a functional B12 deficiency - seems quite counter intuitive that more B12 should be the answer but that seemed to be the case for the person reported in the article.

I don't know for sure if I have a functional deficiency but I do know that I have to keep my B12 levels astronomic in order to feel well - symptoms actually start to return on the day of a maintenance shot.

Good luck with your GP

Thank you. I cant see the 2nd article. It's not there when opening the link......

Gambit62Administrator in reply to Poppyfields65

Sorry - I'm not having a problem. May be a question of browser or may just be slow to load though I don't have a problem with it loading.

I'm using Chrome as my browser at the moment if you have that on the machine you are using may be worth trying it.

Hi. Yeah I'm using chrome but I'm on my phone. Will try the pc later and different browsers. Thanks.

I'm finding it difficult to find info about it except the first link you provided which is on alot of sites.

I have functional B12 deficiency. It's a fault with the transporter called Transcobalamin. It picks up the B12 from the blood and takes it across into the tissues. The treatment is weekly B12 injections. The idea is to flood the bloodstream with lots of B12 even though only a tiny amount will be transported. You could try low dose lithium orotate 5 mcg which aids the transport .

Allyson1 in reply to Lilnicki

Does this imply a lithium deficiency?

Allyson1 in reply to Lilnicki

Very interesting, did you have particular tests to diagnose it?

Is it an autoimmune attack on transcobalamin?


My GP has now prescribed weekly injections with a review in July. I've already had 5 jabs at 2 weekly intervals. I haven't had the "loading doses. " Does that matter do you think?

I've been reading a little and watching some YouTube videos. Is the transportation problem with transcobalamin from the blood into the tissues the same as "transcobalamin deficiency" I've seen this talked about on a video and on a government study of active b12, but it says it is diagnosed in young children due to severe symptoms!! I'm 50!


I have similar things:

-slow to respond to weekly loading doses

-low appetite/weight loss

-neurological problems

- symptom onset with levels still in the 400s

- short term improvement after shots-days or hours

Sadly I don't have advice because I'm as confused as anyone. All I know is I really feel I need more b12, I just can't get enough. Raw liver sounds really delicious right now

Thanks for that. I've re read the lab report in order to translate it in preparation for my GP appointment tmw and I've noticed it says "functional b12 deficiency / insufficiency at the tissue level."

So, I'm now assuming it means functional b12 deficiency could be the cause or there maybe another cause???? PA maybe?? With PA... Does it not get into the tissues aswell?

I do have Inflammatory Bowel Disease aswell so I guess this could be a reason. I'm waiting for a ct scan so maybe this will show if anything is wrong with the terminal Ileum stopping absorption....

Either way treatment is the same.... Just getting the all important dosage right? Which appears to be the difficult part depending on who your doctor is.....??

Should I be seeing a hematologist? I'm already waiting to see a Neurologist about dizziness and pins and needles, headaches etc. I also get brain fog etc.

Sorry, lots of questions there. I need to learn more I think.

Are there any books recommended?


Definition for PA is a tricky one because not all medical professionals can agree on it even. If you mean problems with intrinsic factor, then that's not likely given your serum level appears normal ie the intrinsic factor passed your B12 from your stomach into the blood stream no problem. It does look like your issue is Functional ie the transporter that takes from the serum to the tissues is not working.


OK. Yes I was referring to IF and what you say makes sense. Thanks. I suppose I have to see what my GP says tmw and go from there.

I just watched the video. Very clear explanation. Thanks again.

Children born with Transcobalamin DEFICIENCY are very sick....... Transcobalamin INSUFFICIENCY will still transport small amounts of B12

Got it. Thanks

Mickyaela, what was in the injections you were given? There are a few different types of B12, and it is possible you can't convert what was in the injection into an active form of B12.

In the UK, B12 injections are hydroxocobalamin.

In the US they use cyanocobalamin.

Some people have to buy their own B12 ampoules, and they find they do best with methylcobalamin.

I have never been diagnosed with a B12 problem. My serum B12 levels have always been high in range or over the range. However, I had lots of symptoms suggestive of B12 deficiency. I started supplementing with 5000mcg methylcobalamin tablets and it helped me enormously. I also swap the methylcobalamin for adenosylcobalamin a couple of times a week.

Several years ago (when I had no idea what I was doing!) I took high dose B vitamins for a year or two. But all those vitamins included B12 in the cyanocobalamin form. I suspect my body can't convert the cyano-B12 into the active forms, methyl-B12 and adeno-B12. My serum levels of B12 are even higher these days, and is usually recorded as >2000 ng/L.

I'm on cyanocobalamin. I am noticing a little difference in the way I feel after the last few jabs. Some small improvements after about 2 days after the jab but they only seem to last a few days, also noticing that the pins and needles can be a bit worse after a jab and after the one this Wed I've started getting shooting nerve pains. Is that normal?

Like tiny electric shocks ? This is quite common and thought to show the nerves healing.

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