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.
Four months.
Oh, b***y hell! Blow that - I'll be a basket case!
If you're talking about a serum test, then it will be skewed if you're supplementing. But an active test would be OK.
Sorry, could you explain please? - this is the new bit of the recently introduced B12. A bit clueless!
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.
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 ..
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,
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.
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?
Schenks,
24 hours after the injection.
Cheers Clutterbug
The test only reveals what is in the blood. B12 is utilised in the cells. Results will be skewed for months if injecting .....
But I'll be able to contrast it with pre-injecting, won't I?
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! 
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!
When to take T3 before blood test - advice please.
Stopping B12 before blood test? 
How long does a coeliacs blood test take to come back?
Levo before a blood test
t3 before blood test
