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Pernicious Anaemia Society
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B12 Mean Corpuscular Volume

50 yr old male B12 Vitamin Serum 155ng/L range 130.00-800.00ng/L

Serum Folate 12.2 ug/L Range 4.00-20.00ugL I have visited my GP and mentioned my B12 Serum Test Result Concerns,

My GP explained that my result is normal as my (MCV) Mean Corpuscular Volume is 91fL

which is right in the Middle of the Range 80.00-100.00fL.Which would likely be elevated in B12 diagnosis.Would anyone on the forum agree with this as it is quite confusing.

GP has agreed that i should check B12 Serum once a year due to my Mothers Pernicious Anemia.

When i took the online B12 deficiency symptom test i scored 9+ at Pernicious Anemia Society website

from a link kindly provided by forum member.

I asked GP about Methylcobalamin sublingual Tablets for a family member to take between injections

and the GP said they were unaware of any benefits taking these or any supplements of B12 in between Injections of 3 months,as there are no clinical trials on this in the UK

And also said you can't get Methylcobalamin sublingual in the UK and asked where i had seem them.

I mentioned only Overseas sales that i had seen.



24 Replies

Hi only 30% people don't get anaemia with B12 deficiency and most GPs don't know this but it is well recognised in research. There is an inverse correlation between anaemia and neurological symptoms so people with bad anaemic are supposed to get less neuron symptoms and vice versa. No-one understands this.

I had low B12 which GP was not going to treat because I wasn't anaemic but I had a lot of neuron symptoms which the majority resolved in 8 weeks of every other day treatment with hydroxocobalamin 1mg im

I would recommend getting an active B12 checked at St Thomas if you have not taken any supplements yourself.

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Hi Secondchance

thanks for taking time to reply and for your recommendation too.

Good Luck



Interesting reply Secondchance, would you mind to give me more details on which department at St. Thomas's to go through to get an active B12 test, I know my boyfriend has an issue with B12 but need to have the evidence?



This post includes advice on tests and how to order them. I read somewhere that they are no longer asking for GP referral.



that b12 result is very low, especially as your mother has PA I would insist he checks for PA.




Hi Ollie7horse

I earlier worked out that 155ng/L converted to pmol/L, ie ,

multiplied by 0.738

equals 114 pmol/L ,which i did explain to my GP , to convert to pmol/L

then work out 20% of the 114pmol/L = 22.87 GP thought 114pmol/L was fine!

So i think an Active B12 Holo-transcobalomin test would be a good idea to be checked at St Thomas

as recommended by Secondchance

Thanks for you kind advice.



I found this interesting article at Patient co uk,


Serum vitamin B12 is the most commonly used method of establishing B12 deficiency. In general, levels <111 pmol/mL reliably indicate deficiency. Neurological deficiency or anaemia is usually evident in patients with levels <89 pmol/mL. False positives (low levels in the absence of deficiency) can occur with pregnancy, folate deficiency, myeloma,[7] and excessive vitamin C intake.

i'm 114 pmol/mL which like you say is low but why doesnt the GP see this?


Yes it would be wise to request intrinsic factor and parietal cell antibodies but again GP may refuse as "normal" B12. Catch 22


Unfortunately GPs aren't omniscient.

Even more unfortunately most of them either aren't aware of this or are incapable of admitting this so they are perfectly capable of spouting as much rubbish as the rest of us.

Even more unfortunately their position means that people tend to trust them and think that what they must be saying must be 100% correct.

I remember years ago a GP telling me flat out that there wasn't a test for carpal tunnel syndrome - which I had been recommended to ask for and given a leaflet about by occupational health at work. However, I'm at the not trusting doctors end of the spectrum anyway so ....

Of course you can get methly b12 as sublingual tablets in the UK - it is a vitamin and it isn't regulated in the UK as a medication would be. The only reason why injectible B12 is regulated is because the prescription only rules in the UK apply to all injectible substances.

Personally I'm a bit sceptical about some of the information on patient.co.uk, eg the statement on B12 something on the lines that 'a very few people have problems with the frequency of injections and experience symptoms returning before maintenance shots' as that so does not chime with my own experiences and in general where I find people who don't question the regime they all know when their shots are due because the symptoms start to return ... and don't get me started on the questionnaire on depression (not sure if that is patient.co.uk to be fair.

The NICE guidance on B12 is hopelessly confused and confusing for GPs - really doesn't do anything to dispel the confusion over B12D and anaemia and probably even makes it worse. Unfortunately they don't have the time to go into other ancilliary guidance such as BCSH ... and lets face it even a few haemotologists don't seem to be fully aware or understand it.

The best doctor I ever saw - and one of the few that I would trust - a neurologist specialising in migraine - had the strength and integrity of character to be able to admit that he didn't know everything and nobody did and most of the time it was a question of we do it because it seems to work. Okay so it is an approach that has its dangers but it's honest and it's open and that is soooooo what is missing in these days of being driven by checklists, 5 minute appointments, dealing piecemeal with symptoms rather than dealing holistically with the patient and looking for underlying causes - treating labels as if they are conditions - because that is what GERD is, that is what depression is ....

Sorry I've gone through today on much less B12 than I normally have and starting to get a bit ratty as a result.

Have some sympathies with GPs in terms of not being able to know everything but do rather lose that when you see how unwilling they are to actually work with patients to address concerns or actually listen and take notice when they provide them with information.


Hi Gambit62 sorry to hear your not too good today I do hope you feel better soon.

Thanks for your contribution which i really did find very useful especially as you mentioned Carpal Tunnel which i was tested and was found to have in my left arm.

Which i will make a note of.You have raised some valuable points and my GP did mention about being careful what you read on the internet about B12 Deficiency!

You have to fight for the right to be heard for treatment and if it has to be private treatment with an Active B12 test i will just do it like you say we trust the GP

But out of all the Doctors over the years my mothers was diagnosed very late

through no fault of her own, which is terrible.

Thank-you very much for generous your help Gambit62



"My GP explained that my result is normal as my (MCV) Mean Corpuscular Volume is 91fL"

If you have a co-existent low level of iron ( I can't see a ferrritin result) this could explain why your MCV is "normal". Low iron makes blood cells smaller, low B12 makes them bigger therefore if you have low levels of iron and B12 your MCV results can appear normal.

Have you read the following documents/books. You may find them useful.




Could It Be B12 by Sally Pacholok

Pernicious Anaemia; The Forgotten Disease by Martyn Hooper

1 like

Hi Sleepybunny thanks for the links and your explanation.

much appreciated.

I can't seem to see Ferritin on my Full Blood Count any ideas what i'm looking for and how its expressed as in short in Test.

Thanks agin



Serum ferritin would be a separate test to the full blood count. I'm surprised they tested B12 and folate without testing ferritin.

Have you had your iron levels checked at any point in the few years?

Some patients are able to get Homocysteine tests and MMA tests.

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Hi again Sleepybunny I see so the Ferritin test would be a seperate test

So the Ferritin test would be a test to do before the ActiveB12 Test then?

Yes I have had a few Blood tests checking iron :

April 2012

HB 13.8 g/dL Range 13.0- 18.0

RBC 4.46 (10/12L) Range 4.50-6.50.....Low this is year Before Operation NOT given iron from GP.

in 2013 after an operation where i needed a transfusion of 3 Packs .At that time my Test for iron was as follows:

2 July 2013

HB 144 Range 130-170gl

RBC 4.84 Range 4.5-5.5*

23 July 2013

HB 93 Range 130-170gl...... Low

RBC 3.12 Range 4.5-5.5*...... Low

After Leaving Hospital Given Oral High strength ferrous sulphate Iron Tablets for 3 months.

I remember going Back to normal values after Blood test.

May 2015

HB 139 g/l Range 135-175gl

RBC 4.68 Range 4.50-6.50

Thanks for your kind helpful advice Sleepybunny,



Hi these are full blood count results. An iron profile gives ferritin, serum iron and transferrin which is a separate test.

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Hi Secondchance thanks for informing me of this.



MCV (unless definitively low or high) needs to be considered in relation to other factors/results. Low B12 tends to cause high MCV; low iron tends to cause low MCV. Concurrent low B12 and low iron can result in a very middle-range MCV. In that case you would expect a high Red Cell Distribution Width (RDW).

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Hi Helvella ,Thats interesting about RDW (RBC) thanks for your explanation

so as i'm in the Mid Range MCV 91fl (Range 80.00-100.00fL) from the results i posted for the Blood Count in my recent post RBC are slightly on the low side and not High.It appears from what you say that i have a Normal Result ,but possibly just naturally have a low B12 result of 114pmolL (155 ng/L)

And this could be "normal" for me.

Thanks for your reply Helvella



Do you know your RDW? It isn't always measured.

If your RDW is high, it means that you are very likely BOTH B12 deficient AND iron-deficient.

I think your B12 is so low that you are B12 deficient.

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Hi Helvella ,Yes i have A RDW in Full Blood Count

RDW 13.1 Range 11-14.50

Mid Range MCV 91fl (Range 80.00-100.00fL)



Not dramatic, but certainly pointing in the direction of iron-deficiency.

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thanks for the reply Helvella , could you explain What i need to highlight to my GP that they

are not getting please.



This is quite a thorough overview:


And good provenance!


Thanks for the kind input and Link


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