Does taking oral B12 bias a B12 test high for someone with PA?

[AirAl]

Maybe a dumb question but does taking oral B12 bias a B12 test high for someone with PA?

My doc has asked me to try oral B12 prior to my next re-test to "see if it works". She said that sometimes diet absorption isn't enough for some people and supplements help. She's talking B12D in general, not PA specifically I assume.

I'm worried that I'll get a false positive. Does the B12 serum test give you effective B12 that you've absorbed properly (orally or via injection)? Since I source and self-inject, I guess I'll manage by symptoms either way. I guess this way, if my B12 goes low despite loading B12 orally, I'll know it's likely PA. Alcohol would be ruled out because I'm abstaining from that as well (unless alcohol use can do something permanent to one's B12 absorption).

[deniseinmilden]

Yes it does, unfortunately, as some gets through which raises serum levels but not enough to be effective.

Symptoms are your body's way of telling you something is wrong and needs fixing so you have to go by your symptoms, rather than blood test results, to keep you healthy.

If you SI then do that at a frequency that keeps you feeling well and remember to take supporting supplements - a broad spectrum multivitamin and mineral supplement plus extra folate, potassium, magnesium and maybe iron and vitamin D from your diet.

[fbirder]

No, it doesn't.

There is no such thing as a 'false positive' serum B12 test. It tests for B12. If it finds B12 then it doesn't matter how it got into the body, the test cannot tell the difference between oral B12 and IM B12, and nor can the body.

So, if you take oral B12 and your blood levels are raised to the same levels as you would get from an injection, then the oral B12 will do just as much good as an injection.

The problem comes if you have some sort of absorption problem (like that caused by PPIs or metformin or unknown) that doesn't completely block B12 absorption. Then you may find that oral B12 does raise blood levels into the 'normal' range, but not high enough to eliminate symptoms in you.

These tests that show that 'people with Pernicious Anaemia' can absorb oral B12 are, as far as I can tell, faulty. Many of them assume that anybody with a B12 deficiency has PA. Most assume that anybody with a non-dietary deficiency has PA (and they determine if it is dietary by questionnaire). None of them seem to look at other known factors that may cause a deficiency but that aren't PA. And, obviously, none look at possible unknown factors.

I wish it were true that oral B12 is just as good as injections. But I've tried every tablet, lozenge, spray and patch - none of which work.

That's why people need to try things and see what impacts their symptoms.

[Gambit62 Administrator]

I see you have had replies going on both directions.

The answer is rather complex and in part that it depends on the dose that you have been given. The usual treatment for dietary B12 deficiency is 50mcg (think x2 per day). If you have PA then, even with passive absorption you won't be able to absorb enough B12 from the tablets for it to make a difference.

If the tablets are 1000mcg + then it is possible that they could affect future tests as you may be able to absorb enough through passive absorption to either stop levels decreasing further or make them rise ... but in terms of a treatment that would enable you to recover they would take a very long time to really have enough of an effect on your B12 levels. If you have neurological symptoms it is important that these are treated quickly.

Studies into absorption of high dose oral B12 show a huge variation between individuals - and it wasn't effective for everyone. Literature reviews analysing results on the basis of cause of B12 deficiency show that rates for high dose oral being effective are around 70-80% independent of the cause of deficiency - including pernicious anaemia.

[Gambit62 Administrator in reply to Gambit62]

this is a link to a recent literature review on oral v intramuscular in treating patients with B12 deficiency caused by absorption problems - though it doesn't differentiate PA from other causes.

ncbi.nlm.nih.gov/pmc/articl...

[AirAl]

Thanks for the replies. We'll see. I thought I had some B21 pills on hand, but all I have is a 5000mcg pill that you're supposed to do sublingual then swallow the rest. I took one the night before last. All I felt was a splitting headache (rare for me) which wasn't necessarily the B12 pill. I might just go pick up a normal pill.

[Gambit62 Administrator in reply to AirAl]

was the pill methylcobalamin? lots of people don't respond well to methylcobalamin.

If your GP didn't give you a prescription then I would suggest sticking to doses of 50mcg or less - or even a multivitamin containing B12, though on the whole your GP seems very confused about what is going on. it is true that as you get older lower stomach acidity can affect absorption and supplementing with 50mcg-100mcg a day can help in that instance.