Confused over b12/IFAb results - what to do next!

Hello nice people,

I'm new here on PAS, I have posted on Thyroid UK before as I have hypothyroidism (Hashimoto's).

I had some private tests done for thyroid levels which included vitamin checks too and they showed the following:


B12 serum 179.7pg/ml (191-663)

Folate serum 9.61ug/L. (4.6-18.7)

Vit D 25 OH 18.1nmol/L. (50-200)

Ferritin 19.28ug/L. (13-150)

CRP high sensitivity- 8.1mg/L (0 - 5)

I supplemented with sublingual b12 200ug/every other day for 2.5 weeks until I went to see my GP. My neuro symptoms were increasing and I thought I might need b12 injections. Members on thyroid uk had advised me also to ask for GPC and IF antibody testing. Well, GP, no surprise, didn't think the private tests were reliable, nor that there was any need for the antibody tests ( my grandmother and aunt have PA and there is also coeliac disease in that line of the family- although I tested negative for that) GP did reluctantly agree to test the b12, Vit d etc again.

And this is where my confusion starts! I'd read that you shouldn't supplement 1-2 weeks before b12 testing (and IFAb) so I waited 3 weeks before booking the blood test at the surgery. In the same week I had private tests done for GPC, IF and active B12 and the results are as follows:


Gastric partial cell Ab - Negative

Intrinsic factor Ab - 8.9 U/ml (normal: <6 )

Active B12 - 73pmol/L (25.1 - 165)


B12 serum - 161pg/mL (180-914)

Serum folate - 5.5ng/mL (3.1-20.0)

Indeterminate B12 result. Please correlate with Hb, MCV and clinical picture.

Long term acid suppression is the commonest cause. I have been prescribed H2 blockers and then ppi 's for the last 16 years following diagnosis for hiatus hernia and acid reflux, and when asked about this the GP didn't think I should stop taking these.

Serum ferritin - 19ug/L (13 - 150) Low normal ferritin must be considered with clinical context and other haematological indices. Ferritin increases in response to inflammation - iron deficiency can then be masked.

Serum 25 OH Vit d3 - <30nmol/L Result: severe vitamin d deficiency.


Haemoglobin estimation: 138g/L (115 - 165)

Total white cell count: 5.30 10*9/L (3.40 - 11.0)

Platelet count: 245 10*9/L (140 - 450)

Haematocrit: 0.433 (0.350 - 0.470)

RBC Count: 4.77 10*12/L (3.90 - 5.60)

MCV: 90.8fl (80.0-102.0)

MCH: 28.9pg (26 - 32)

MCHC: 319g/L (300-360)

Red blood cell distribut width: 14.4% (11 - 16)

Neutrophil count: 2.80 10*9/L (1.70 - 8.00)

Lymphocytes count: 1.80 10*9/L (1.00 - 4.00)

Monocyte count: 0.50 10*9/L (0.20 - 1.50)

Eosinophil count: 0.20 10*9 /L (0.00 - 0.50)

Basophils count: 0.00 10*9/L (0.00 - 0.10)

I'm confused as to how I got a mid range Active B12 result and a low Serum B12 result within a day of each other. Could the IFAb result be a false positive because of the b12 supplements I took three weeks earlier?

I have no idea yet how to interpret the FBC results - do they look ok?

My GP has prescribed Desunin 4000IU daily for 10 weeks then 800IU daily until retest in December for the Vit d deficiency, but nothing regarding the B12 - I still have the neuro symptoms - pins and needles, mental fog, memory loss, episodes of fatigue, dizziness, blurred vision etc

Any help gratefully received 😀

2 Replies

  • unless the lab that did the IFAB test were using an assay that's over 30 years old (unlikely) then three weeks should have been plenty of time, especially as your serum B12 was that low.

    Obviously your sublingual B12 isn't doing much at all - otherwise one would have expected your serum B12 to be quite a bit higher, even after three weeks. You really need to stop supplementing for a few months before a B12 test.

    I've no idea why the 'active' B12 test result disagreed with the two serum B12 results.

    I can't believe your GP is ignoring the IFAB test. That is just criminal. You have low B12, you're positive for IFAB, you have a family history of PA - all point to you also having PA.

    I'll bet he's yet another idiot that thinks that you need large red cells to have PA. He is wrong. Download my summary document - - which links to several expert dosuments and includes summaries of the key points, one of which is the fact that PA can occur without presenting with haematological symptoms.

  • Thank you fbirder, so low b12 and positive IFAb results are more than enough for me to be offered b12 injections?! I was worried that my FBC results looking ok meant that I had not understood something...... I will study the frankhollis link - I have another gp appointment next week and this has made me feel much more confident about standing my ground.

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