Pernicious Anaemia Society
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Help with B12 please

Hello, I have been advised to post here after posting on Thyroid UK re B12 levels. I have autoimmune thydroitis and low Vit D. In July Medichecks thyroid panel showed Serum B12 as 91 (140-724) GP thought injections not needed and prescribed cyanocobalamin. I started B complex now Sept tests now show Active B12 as 37.3 (25.10-165.00) can you advise what level I should be aiming for I'm presuming near the upper part of the range and which supplements are recommended? Many thanks.

10 Replies

It looks like the two tests Newhyp1 lists are different tests. The first is a serum B12 test and the second is an active B12 test. The two can't really be compared to each other, though the active B12 test result being in range does indicate that the tablets are mostly likely helping.

My question is how are the symptoms? Do they linger or have they gone away? If the symptoms have gone, then you're doing well on the tablets and can probably stick with what is working. If the symptoms haven't gone, then upping the dose might be necessary. Out of curiosity, did your doctor explain why injections weren't needed?


Hi, he just said he didn't want to do it straight away, hard to tell symptom wise as thyroid levels not anywhere near where they need to be so they overlap also had low vitamin D so they think it's that.


Newhyp1 - are you a vegan/have very little meat/fish/dairy/egg in your diet - the treatment you have been given for B12 deficiency is that for a dietary deficiency. B12 is only found in animal products.

as comments above it is very difficult to see what is going on from comparing a serum B12 with an active B12 test - though your active B12 is in range.

Using either of these tests as a guide to where your levels need to be is a flawed strategy as they aren't direct measures of what is happening with B12 in your cells - just of the amount in your blood. What really counts is symptoms.


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Hi, unfortunate for me they changed tests in between my first and second one. I found out from the first I have autoimmune thyroiditis so have been gluten free for two months, no not vegan eat meat and eggs and now eat more dairy than before going gluten free. Hard to say with symptoms as TSH levels are still high I've still got sore tongue and fatigue leg weakness but symptoms are put down to underactive thyroid and low vitamin D GP didn't test B12.


suggest that you look at one of Sleepybunny 's replies and think about contacting the PAS directly, given the low B12 result - is quite unlikely that you aren't B12 deficient with that level, even given the vagaries of the serum B12 test.

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Thank you, will do.



Hope you find the answers you need.

I've assumed you are in UK. It's helpful to know where a person is in the world as patterns of b12 treatment vary from country to country.

Serum B12 as 91 (140-724)

Your B12 result seems very low.

UK b12 documents

I'd suggest reading the following...

1)BSH Cobalamin and Folate Guidelines

Flowchart from BSH Cobalamin and Folate Guidelines

Flowchart makes it clear that in UK, people who are symptomatic for B12 deficiency should have an Intrinsic Factor Antibody test and start initial B12 treatment. IFA test can help to diagnose PA but IFA test is not always reliable and it is still possible to have PA even if result of IFA test is negative/normal range. My experience is that some UK GPs are unaware of the possibility of Antibody Negative PA.

Flowchart outlines when PA (Pernicious Anaemia) and Antibody Negative PA can be diagnosed.

2) BMJ B12 article

Emphasises need to treat symptomatic patients even if B12 normal range in order to prevent neurological damage

3) BNF British National Formulary Chapter 9 Section 1.2

Outlines recommended B12 treatment in UK. GP will probably have a copy of BNF on desk.

UK B12 treatment info is also in BSH Cobalamin and Folate Guidelines, about a quarter through guidelines.

Sometimes oral cyanocobalamin tablets are prescribed to treat dietary B12 deficiency but for B12 deficiency linked to absorption problems then injections are recommended.

You mention eating meat, eggs, dairy so it becomes less likely that low B12 is due to diet and more likely that there is an absorption problem. Do you also eat fish and shellfish?

Standard UK b12 treatment for someone with absorption problems is 6 loading jabs over 2 weeks followed by a jab every 3 months.

UK b12 treatment for someone with B12 deficiency with neurological symptoms is a loading jab every other day for as long as symptoms continue to get better then a jab every 2 months.

Lots more b12 info in pinned posts on this forum. I found fbirder 's summary of b12 documents helpful. Link to summary in third pinned post.

Do you have any neurological symptoms eg tinnitus, tingling, pins and needles, memory problems, balance issues plus other neuro symptoms? A lot of UK people on this forum struggle to get correct level of tretament if they have neuro symptoms.

Lists of B12 Deficiency Symptoms


What does GP think is causing your low B12?

What the GP thinks is the cause could influence the level of treatment you receive. From the level of treatment you've had so far, I've assumed GP thinks your low b12 is due to diet. Is GP aware that you eat meat, dairy and eggs?

Risk Factors for PA and B12 Deficiency


"have autoimmune thyroiditis so have been gluten free"

Having an auto-imune condition can increase the chances of developing another one eg PA, Coeliac disease etc

Were you tested for Coeliac disease before going gluten free? As Coeliac disease can affect the gut it can lead to absorption problems with some nutrients eg B12

Do you get copies of all your blood test results? In relation to b12 I look at serum b12. folate, ferritin and full blood count.

Access to Medical Records (UK)

Blood tests

B12 books

"What You Need to Know About Pernicious Anaemia and Vitamin B12 Deficiency" by Martyn Hooper

Martyn Hooper is the chair of PAs (Pernicious Anaemia Society). Book is up to date with UK B12 guidelines.

"Living with Pernicious Anaemia and Vitamin B12 Deficiency" by Martyn Hooper

Has several case studies.

"Could it Be B12; An Epidemic of Misdiagnoses" by Sally Pacholok and JJ. Stuart (USA authors)

Very comprehensive book about B12 deficiency with lots of case studies.

B12 blogs

May be relevant stories on Martyn Hooper's blog about PA and B12 issues.

Also an interesting blog on "B12 deficiency Info" website.

PAS (Pernicious Anaemia Society)

If you suspect PA is a possibility, may be worth joining PAS. They can offer support and information.


PAS tel no +44 (0)1656 769 717 answerphone

Unhappy with treatment (UK info)?

Link about writing letters to GPs about b12 deficiency


HDA patient care trust

UK charity that offers free second opinions on medical diagnoses and medical treatment.

I am not medically trained just someone who has struggled to get a diagnosis.

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Thanks for all that. A lot to check out and take in. Yes I'm in the UK. All came about since Christmas when I had a terrible whooping type cough which didn't clear up. End of Jan showed TSH high waited 3 months for re-test when I felt terrible, fatigue lots of symptoms, memory etc tests showed still high and low Vit D after 3 months so diagnosed hypothyroid and started Levo and Vit D. Did private bloods in July which showed thyroid antibodies and low B12 hence dr prescribed cyanocobalamin and requested endo referral. Going back to GP next week will find out what he thinks about the B12 now. GP only test TSH and Vit D so far. Awaiting endo appointment end of October. I have since read about testing intrinsic factor but have seen that no supplements should be taken prior to this. Will GP test do you think now? I do eat fish not shellfish though plenty of eggs as have chickens. I don't eat liver but must start. I did have symptoms which could have been hypo or Vit D deficiency and have had sore tongue now since May which Dr thought was high stomach acid and prescribed PPI advice from Thyroid forum suggested hypo = low stomach acid so I don't take these now. Haven't been tested for coeliac don't suffer with symptoms but again advice seems to be going gluten free will help reduce antibodies in long term since stopping I do not get the bumps on my fingers so will continue. Other tests were:

July folate serum 2.98 Sept 7.48 (2.91-50.00)

July ferritin 22.81 Sept 20.1 (13-150.00)

Have GP appointment next week so will try to read up and go in knowing what to ask.


"have had sore tongue now since May"

Glossitis (inflamation of the tongue) is a symptom associated with B12 deficiency.

Glossitis is mentioned in BSH flowchart (link in post above).

Might be worth posting blood results on Thyroid UK forum and asking about optimal levels of iron for thyroid function.

"I have since read about testing intrinsic factor but have seen that no supplements should be taken prior to this. Will GP test do you think now?"

I'm surprised that GP has not already ordered an IFA test....especially as it is recommended in BSH Cobalamin and Folate Guidelines. Some UK Gps may not have read the BSH Cobalamin and Folate Guidelines. I gave my Gps a copy of them.

Having an IFA test close to a B12 injection can lead to a false positive result. Some doctors suggest leaving at least 2 days between a B12 injection and an IFA test. See link below.

PAS (Pernicious Anaemia society) might be able to point you to info on Intrinsic Factor Antibody test.

Article about low stomach acid

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Thanks I'm glad to hear that I didn't think it was high acid and it's been driving me mad feels like I've constantly burnt it on a boiling drink! Will go armed with information and hope it doesn't go down like a lead balloon.


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