Thyroid UK
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How to interpret B-12 results?

If anybody can provide some guidance on this issue, it would be much appreciated.

Have another appointment with the Dr tomorrow and people have suggested that I get a B-12 test as my FT4 low and TSH a little low as well.

Not sure what I should be looking at on my full blood counts to see whether or not a B-12 test has already been done.

Many Thanks

12 Replies

A B12 test is NOT a part of a Full Blood Count.

Two figures on many FBCs are Mean Corpuscular Volume (MCV) and Red Blood Cell Distribution Width (RDW) - which can hint at B12 deficiency but only real B12 tests prove it.

If you live within travelling distance of London or are willing to pay for a private test, you might consider getting an Active B12 test which is seemingly better able to identify B12 deficiency.



So my MCH levels which are lo 27.6 (28-33) simply mean that I am slightly anaemic and therefore to establish B-12 levels a further test is needed?

Thank you



Yes - a further test is needed.

Did you have MCV and/or RDW on your results?

(This forum is being a real pain - have deleted both your and my duplicated responses here.)


I thought it was just me, as it kept timing out lol.

tbh there are a few readings the Dr advised it was a full blood count (liver, kidney and oestrogen levels etc).

so in answer to your question (sorry) there are HB's, WBC's, Platelet, RBC's, Haematocrit, MCV, MCH and MCHC.

Scanning the list for abnormalities it just shows low levels of MCH, high pottasium and low FT4's.


a low MCH can indicate you are well hydrated


Dr has agreed to the additional tests above - even though he thinks they are a waste of time (rolled his eyes when he realised that I was using this and the British thyroid Foundation sites!!!

However he did check my previous TSH levels and they ranged: -




0.9 (2007)

to which I replied that maybe it would have been interesting to see what the FT4's had been like then.

Decided to take my chance with these and a referral to an Endo.


Different labs use different ranges. The range mine use for example is 180-900. My endo said my level was 'fine and in range' at 219. However, studies are showing that the lower end of the B12 range should be no less than 500 and most feel optimal at around 800. Tell your GP that you are researching your thyroid disease and request a B12 test (arm yourself with knowledge and don't take no for an answer). Even though I was 'in range' my endo agreed that perhaps I would feel better at a higher level and I insisted that my treatment was started with injections as opposed to oral supplements. I have had 6 (3 per week for 2 weeks) and will have another blood test in 2 months time and depending on what the level is, maintenance shots are available every 3 months (or more frequently if needed). My nurse actually said that GPs prefer to prescribe shots as they are much cheaper than prescribing oral supplements.


If having B12 injections you need to make sure that they are Methylcobalamin and not cynabalamin ( not sure if i've spelt the latter correctly) I've read that the NHS uses the surprise there then......but i could be wrong, just check and make sure.


UK prescribed injections are hydroxocobalamin. NOT cyanocobalamin.

The British National Formulary says this:

The BP directs that when vitamin B12 injection is prescribed or demanded hydroxocobalamin injection shall be dispensed or supplied

Free registration is required to use that link.

Note: That says shall - which gives the pharmacy and medic no choice.



so is it acceptable and ok to use then?


One thing that is quite clear, different people have different views.

My own knowledge is limited and I do not feel able to offer advice as to the appropriateness of hydroxocobalamin as against methylcobalamin- either orally or injected.

Clearly most high dose oral supplements are methylcobalamin.



Hyrdoxolcoalbamine works fine for some people it depends if the person can convert to methycoalbamin satisfactorily (via cynacoalbamine). Hyrdoxo works fine for me for instance.

Be aware that any oral supplements need to cease for two month and shots for 3 months to get an accurate B12 test be it 'active B12' or serum B12.

Go to the Pernicious Anaemia society page for in depth and detailed info.

There is something awry in your tests, keep badgering your gp, and posting here to get to the bottom of it. Or go to a good endo....!

What is GP's explanation of high Potassium??

Your TSH is creeping up, What are your FT's?

How do you feel?


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