B12 serum levels and IFA test?

Hi , I’ve just had some blood taken and they are going to check for Intrinsic Factor. I had been supplementing daily with 5000 ug Methylcobalamin but stopped two weeks prior to test.

I may have got this wrong, but I thought the GP said that if the lab saw “normal” levels of B12 in my blood (I.e. anything above 180), they might not do the test. Given that I’ve been supplementing for over a year, I would imagine this is going to be the case.

Leaving aside any skewing of results by the supplements, I was just wondering is it possible to have an IF problem with “normal” serum B12 problems, in other words you have B12 in your blood but it hasn’t got the Intrinsic Factor to process it properly?

7 Replies

  • My serum B12 was 250 when first tested and I was so sure that I had P.A. that I demanded an I.F. test. The lab did it ok and it came back positive - thank goodness, as it is a very inaccurate test and if it had been normal, I would have been up the creek without the proverbial paddle!

    I had all of the symptoms of P.A. despite a 'normal' serum level. I'd been supplementing for decades before the B12 levels were tested. (Didn't know at the time that it would make a difference to the results)

  • Thanks, are you now having injections?

  • Yes. Three monthly from G.P. and I jab myself in between as needed - weekly at the moment.

  • I see, thank you. My initial level (before supplementing) was 253. My father also had PA.

  • Both of my parents have P.A.

  • Hi,

    "is it possible to have an IF problem with “normal” serum B12 problems"

    As far as I know, yes..... but I'm not medically trained.

    The PAS (Pernicious Anaemia Society) might be able to tell you more.


    PAS tel no +44 (0)1656 769 717

  • My B12 was off the scale (high) through supplementing sub-lingually and wearing B12 patches when I had the Intrinsic Factor Antibodies test . It still came up positive . But I hear that one should not be supplementing for some time before the test . So I don't know what to think about that . Once antibodies are there , they cannot be got rid of . One has PA for life .so one should have injections for life . I assume that now I inject weekly I always have very high B12 in my blood , but Antibodies must still be present.

    Intrinsic factor is produced in the parietal cells in the stomach,( as is Hydrochloric acid which is also needed for the absorption of B12 .) The antibodies inhibit the production of IF., as well as hydrochloric acid .They will have been present for some time before the symptoms manifest themselves . Trouble is that the test is terribly unreliable , and doesn't always detect the presence of the antibodieswhen they are there. ( about 50 % of the time)! It's a truly hit or miss test .

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