B12 blood tests after supplementing?

[seamail57]

About 18 months ago after developing neurological symptoms and other symptoms (such as breathlessness) and being told that my serum B12 level was "in range" (224) by my GP, I started to supplement using daily 5000mcg Methylcobalamin tablets and later with a spray also, along with a good B complex with folate. My symptoms improved and all but disappeared, but I have noticed more recently that some have returned so have upped my dose.

I know that a standard blood test will show high levels of serum B12, but which if any of the following tests could I have without the results being skewed by supplementation? I think it's maybe time to push the GP for a course of injections ......

Intrinsic factor

Active B12

MMA

Homocysteine

Parietal cell antibodies

MTHFR gene (my late father had PA)

Thanks

[clivealive Forum Support]

Hi seamail57 given your family connection with P.A I would ask to have your Intrinsic Factor tested. You may have to lay off supplementing B12 for a couple of weeks.

I'm not a medically trained person but there are other on here who can give you good advice.

[Gambit62 Administrator]

IFA is a specific test for PA as a cause of a B12 deficiency. You would need to stop supplementing for about a week before the test though as supplementation can cause false positives. If the test comes back negative that isn't conclusive proof that you don't have PA as it produces false negatives 40-60% of time depending on the assay method.

Active B12, MMA and homocysteine unlikely to be useful unless you lay off the B12 for 3-6 months and may not be effective then.

PCA isn't a recommended test in the UK anymore as it is prone to false positives.

MTHFR is actually a group of genes that control methylation processes in the body. It affects ability to process folate much more than it affects ability to process B12. It is not related to PA as a cause of a B12 deficiency.

[seamail57 in reply to Gambit62]

Thanks Gambit62 for your comprehensive reply.

From what you say, most of the tests will need me to stop supplementing and even the IFA test might not be conclusive. I think the best way forward is to try and persuade my GP to start a trial of injections and see if my symptoms recede.

254 and "in range" though !

[Gambit62 Administrator in reply to seamail57]

level of 254 despite very heavy supplementation - the amount you are taking daily is north of 1000x RDA (or whatever it is called these days).

[seamail57 in reply to Gambit62]

254 was my level *before* I started taking any B12 supplements (about 15 months ago). I re-tested my blood 5 months ago and my serum level was up to 1100 (but no idea how much of that is "active" of course!).

[Gambit62 Administrator in reply to seamail57]

for most people active v inactive is a bit of a red-herring - the ratio is about 20% active - it will only vary for a very few people and I think that is down to some rare genetic factors.