How long before blood test to stop B12? - Thyroid UK

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How long before blood test to stop B12?

Schenks profile image
23 Replies

I know that my levels will be high, but is it the usual 24 hours to stop B12 before the blood test (usual as in thyroid meds)? I inject SC alternate days and take the complex which includes folate every day. So should I hold off the tabs and the injections for one day or longer?

Thanks.

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Schenks
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23 Replies
greygoose profile image
greygoose

Four months.

Schenks profile image
Schenks in reply to greygoose

Oh, b***y hell! Blow that - I'll be a basket case!

greygoose profile image
greygoose in reply to Schenks

If you're talking about a serum test, then it will be skewed if you're supplementing. But an active test would be OK.

Schenks profile image
Schenks in reply to greygoose

Sorry, could you explain please? - this is the new bit of the recently introduced B12. A bit clueless!

greygoose profile image
greygoose in reply to Schenks

A serum test tells you what is in the blood; an active test is supposed to tell you what is getting into the cells, and is not affected by supplementation. But, it's expensive, I believe.

Marz profile image
Marz in reply to greygoose

There are two types of B12 in the blood - bound and unbound. One can reach the cells and that is the one that is tested in the Active Test. Still a bit hit and miss though 😊 A bit like the thyroid - best to go by symptoms ..

greygoose profile image
greygoose in reply to Marz

Ah, ok! I was wondering how it manages to measure what's in the cells, but that's what I'd read. That it tests the active B12 makes more sense. But, there's still no guarantee that it is getting into the cells!

Schenks profile image
Schenks in reply to Marz

Yep, thanks for that - I agree.

Schenks profile image
Schenks in reply to greygoose

Oh. Hmm. Pass!

Clutter profile image
Clutter

Schenks,

4 months if you want a baseline test. If you want to see that your dose is adequate just take B12 and folate after your blood test.

Schenks profile image
Schenks in reply to Clutter

It's the adequacy of the dosage - thanks for clarifying that in my mind. But not sure of what you're advising - do you mean just leave the intake out for that day until after the blood test? If so, which day should I have the blood test; the day between subcut, when its just the folate complex, or the day of the injection which would be 24hours or so after the subcut?

Clutter profile image
Clutter in reply to Schenks

Schenks,

24 hours after the injection.

Schenks profile image
Schenks in reply to Clutter

Cheers Clutterbug

Marz profile image
Marz in reply to Schenks

The test only reveals what is in the blood. B12 is utilised in the cells. Results will be skewed for months if injecting .....

Schenks profile image
Schenks in reply to Marz

But I'll be able to contrast it with pre-injecting, won't I?

Marz profile image
Marz in reply to Schenks

Yes as long as you realise it is inflated as a result and of little relevance. It is stated in the Guidelines for Folate and B12 Deficiency ....

Schenks profile image
Schenks in reply to Marz

I think I have come to the conclusion to s*d-it, why bother!

Hillwoman profile image
Hillwoman

Just curious, but why do you want to test serum B12 at all?

On the PAS forum, guided by some recent research and the BCSH guidelines, we usually advise treating by symptoms, because so much can go wrong with cell uptake and metabolism. There's no widely-available test for these processes, only the MMA and homocysteine tests for metabolic by-products.

Save your money and buy yourself some art materials - I just have! :-)

Schenks profile image
Schenks in reply to Hillwoman

It's just to compare the serum levels pre- and post-injecting. It was 310 or thereabouts when tested on the NHS and the GP Nazi guard never informed me. For YEARS! So it's only curiosity, and it would be part of the next blood screen for thyroid -another useless bl***y test but one they insist on!

Hillwoman profile image
Hillwoman in reply to Schenks

It's been so long since I saw the GP for any of my long term ills, I forget that other people are still valiantly chipping away at the rock face...

Schenks profile image
Schenks in reply to Hillwoman

Catching up with you, kid!

TSH110 profile image
TSH110

I cannot bring myself to see my GP anymore! I seem to do ok with that!

Schenks profile image
Schenks in reply to TSH110

Gives me courage!

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