Intrinsic factor test

[Sunnydevon]

My B12 levels are good at the moment but I’m considering having intrinsic factor test today at the doctors. I know the test isn’t that reliable but would my good levels of B12 interfere with test? I read somewhere that they might. I haven’t supplemented with a spray for a fortnight. I have had breakfast cereal and I eat marmite and they contain B12.

[SunnyWorld]

I had a b12 injection 2 weeks before my IF test, I sometimes have marmite on toast I don't take anything else b12 I tested positive.

[Sunnydevon in reply to SunnyWorld]

Thank you for your reply.

[wedgewood]

The test is only unreliable if it comes up negative.If it’s positive , it’s reliable .

[fbirder]

Very high levels of B12 can cause the test to give a false positive.

I'm not sure why you want to test for the antibodies if you have high levels of B12 without injections.

[Sunnydevon in reply to fbirder]

I’m more worried about the atrophic gastritis really as I have digestive issues/acid. Am I less likely to have PA if B12 spray helps with levels.? Thank you for your reply.

[fbirder in reply to Sunnydevon]

Yes, People with PA tend to not get any help at al from the sublingual spray. Which is a shame, as it would be so much easier than injections.

[Sunnydevon in reply to fbirder]

Thank you for your reply.

[teebeevee]

I have read studies that said having a recent B12 injection could create a false positive, but that the injection has to be within 24 hours and the effect wears off after 48 hours.

academic.oup.com/ajcp/artic...

clinchem.aaccjnls.org/conte...

My lab says to wait "at least two days" after an injection to take the test. I have had two positive IF antibody tests, one four days after an injection and another (slightly lower antibodies but still abnormal high) after waiting 11 days after an injection. But my blood levels were obviously high for both, so I am curious to see studies in which high levels not connected to a recent injection causes false positive???