Pernicious Anaemia Society
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Neurologist saying B12 is a 'red herring' - what should I do? :/

Sorry if this seems a bit too much repeated info on my case, but wanted to include some past info, so I could ask an opinion on the problem I have ....

In march I started to experience strong numbness and tingling in my left hand to the point it was hard to feel things - (have had multiple occurrences of this over the years, but put down to iron deficiency by GP)

Coming into April/May my balance was becoming pretty bad but most worrying for me - my vision in my right eye was being affected.

At this point went to the FIRST GP who made me a neurologist appointment without doing bloods.

Went back to a SECOND GP to request bloods - they came back

B12 156ng/L (191-663)

Serum folate 3.6 ug/L (4.6-18.7)

So he noted b12 and folate where low. Said to me that he wouldn't use injections until b12 falls under 100. So packed me on my way with cobalamin tablets 50mg and folic acid 5mg both to be taken once a day for 2 months til my bloods will be checked again. (Didn't take them, but didn't know then what I know now about not accepting tabs if not diet related and neurological involvement)

He also said iron was slightly low but not enough to be treated.

I said I was worried I wasn't absorbing b12 properly and he ordered intrinsic factor and Parietal cell antibody bloods - parietal came back positive, but IF hasn't come back yet

** But this is my BIG ISSUE atm - HELP!: **

I went to the neurologist who has noticed an abnormality in some of the reflexes in my feet and something in my eye - he noted possible central nervous system inflammation pending further investigation and thinks the b12 issue is a red herring.

I'm had my MRI of head and spine today, and follow up with him in Aug.

Yesterday as I was frustrated I went to a THIRD GP. She said she was shocked at the 2nd GPs approach to treatment and she would have put me on injections straight away because of the neurological issues.

BUT, then she read the neurologists report and his thinking that it wasn't a B12 issue. At that point she seemed unsure about going ahead with injections based on this (she knew of the neurologist by reputation and said she respected his opinion.)

I fully admit I think I may have backed her into a corner when she maybe wanted to wait for the outcome of the neurologists findings. So she has me starting loading doses on Tuesday (as it's a bank holiday here in NI on Monday)

Did I do the wrong thing? I am so confused as what to do - should I go ahead with the injections or wait til the neurologist finishes his tests?

Would b12 affect any further tests, I.e lumber puncture if I needed it?

8 Replies

Hi Laurabeebee,

Yes B12 injection will affect any further investigations of a diagnosis of B12 def, as you will not be B12 def anymore after you start treatment, it will not affect something like IF antibody test. Idealy you have bloods taken before treatment and this sample is then frozen to be used for any other investigations (as I believe is recommended in the BSCH guidelines B12 and folate def‏) . This option is still possible, but if your surgery will do that, has the abilety to freeze a sample I would not know. You still have a choice, wait until all investigations have been completed and possibly ending up with a diagnosis and treatment or start injections now as you obviously are deficient. It depends on how bad you feel I suppose what decision you take..

Kind regards,



Hi Marre, I was more worried that if the neurologist had to do further tests to determine the cause of the central nervous system inflammation (not a diagnosis for b12 deficiency) via lumber puncture would having b12 jabs affect the outcome?


Yes B12 jabs could affect the outcome of a bone marrow biopsy, see:

"Bone Marrow Biopsy and Aspiration

Bone marrow biopsy and aspiration are performed to determine whether the marrow is functioning adequately and also may reveal replacement of marrow with tumor, granuloma, or fibrosis. The bone marrow should be obtained before any vitamin B-12 or folate therapy or blood transfusion because megaloblastic changes may reverse rapidly. "

Perhaps it may reassure you that waiting 6 months is not going to be that terrible compared to getting the right diagnosis and treatment you may need; I started having more investigations some 5 years into treatment on once ever 3 months NHS B12 jabs as I felt dreadful one month out of 3. Saw heamatologist end sept, resulted in diagnosisof folic acid def, and referral to neurologist (march) to then wait for MRI (I was by then unable to stand with feet together, walk a line etc) MRI in August, resulting in diagnosis of subactute degeneration of the Spinal cord and perscribed B12 once every 2 months on my medical file (with 5mg folic acid for 3 months). All these investigations at least meant that all other possible other problems were excluded and I now have for life (slightly) better B12 treatment, with the diagnosis. I had already bought all equipment to start self injecting in Feb of that year, but waited unill all investigations were over before I started adding more B12 etc. At least its in my medical notes now that the once every 3 months treatment is not enough for me, and later on in life I may have to depend on NHS to keep me well, so I believe it is worth waiting to get a diagnosis before self treating, and it did me no harm, but we all are different and I can not tell how much harm it may do you to wait until you have all possible investigations done.

I hope this helps,



Marre, Did that mean you had to be clear of b12 injections before your tests? I am currently taking sublingual b12 and folate


Yes I believe so, self treating will scewer results, that is why I recommend not to self treat until all investigations have finished if you want a firm diagnosis.

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Hi sorry to hear you've had a difficult time. I had a similar experience with the neurologist I saw who was really quite dismissive about B12 as a cause for my symptoms. All I know is that since I started the injections I have been feeling better than I have in years and symptoms have for the most part gone. It is important though to have other things ruled out.

What did you decide to do in the end? Did you go for the B12 injections? Have you had your MRI results?

Bearing in mind the BCSH says 97% sensitivity of having B12 def if B12 is under 200, then your level is very likely to be significant.

Hope you are ok.

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Hi Secondchance :) Thankyou so much very much for the really lovely reply! :)

Yes I went ahead and got the B12 jabs, and yesterday was my last loading dose. Not feeling a huge improvement just yet, but I guess that takes time. How long before you saw a major improvement if you don't mind me asking? :)

Won't get my MRI results until I see the neurologist on the 19th Aug, and then I have a visual evoked response test the next day so he will probably hold out giving me much info until he gets the results of that, unless the MRI gives something clear cut.

I am so glad to hear that you feeling better with b12 treatment - I'm hoping that it is the basis of my problems and nothing more *fingers crossed*

Please keep in touch - I would love to hear about your experiences of all this :)


Hi Laurabeebee

No problem.

Bearing in mind I only had major neurological symptoms just a couple of weeks before I got started on B12 and you had a lower level of B12 and longer duration of symptoms, it may take that bit longer for you. I had alternate day injections initially and noticed an initial improvement in alertness after the first couple of jabs, improvement in numbness after a couple more, but it took 6-7 weeks for my balance, weakness and mobility to improve. My ability to think clearly started to improve after a couple of weeks and this has continued thankfully as that was really scary. Interestingly lots of other things have improved too- dry skin, hair loss, tiredness (which I had put down to busy life, getting middle aged). I got a bit disheartened after a couple of weeks because the improvement seemed slower but glad I persevered. I kept a symptom log each day and then was able to look back and spot improvements.

Good luck with your MRI and evoked responses and next appointment. MRI takes up to an hour if they are doing brain and spine so make sure you go to the loo first is my best advice!

Hopefully you will get some answers but most importantly start to feel better.

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