Medichecks thyroid test and B12

[Pearlteapot]

Hi, I want to test before I go travelling and bought a medichecks advanced with the THANKU25 discount! I was planning to stop Thorne Basic B complex a week before the test to avoid Biotin as advised in this forum.

The medichecks site says to stop B12 for 2 weeks prior to the test and I don't have time to do this and it is not something that I see suggested on this forum. Is that because you should stop if you want to know what your 'unsupplemented' levels are whereas we want to see where the levels are WITH supplementation?

Or does it interfere in some way with the test? Pretty sure it will be okay to test having stopped 6 days in advance but could someone please confirm.

[SeasideSusie Remembering]

Pearlteapot

I queried this back in 2018 when they first started saying that B12 should be stopped, previously they said that biotin should be stopped for one week before testing.

This is their reply:

I have discussed your query with our medical director he has advised the below:

Biotin supplements.

Biotin can affect the results of any test which relies on antibodies to perform the measurement. It is wise to assume that any hormone or vitamin test will be affected, which means that the majority of our test panels can be affected by biotin supplements.

The issue with Biotin only affects people who take high dose biotin supplements. The manufacturers of the laboratory tests define this as 5000 mcg per day or more.

We are recommending people do not take high dose biotin supplements for 24 hours prior to having their blood drawn.

If they are taking high dose biotin for medical reasons (e.g. multiple sclerosis) then a shorter washout period of 8 hours can be used.

Vitamin B12 supplements.

The answer to this depends upon what they are wanting to assess.

To work out whether B12 supplements are meeting the body's requirements we recommend not taking supplements for one week prior to having their blood drawn.

If a customer wants to assess whether they have an underlying B12 deficiency then it can take months (and potentially up to two years) for levels to fall to their natural levels after stopping supplementation. In this instance we would not recommend.

I can also confirm this information will be displayed on our test instructions in the near future.

In my opinion, if you are taking B12 to improve your level and you want to know what you are achieving then I can't see the point in stopping it one week before testing. I would continue up to and including the day before the test. On the day of the test take it after the blood draw.

If you want to know what your body is holding on to B12 wise then you stop supplementing for about 4 months and then test.

As for biotin/B Complex, as we state on the forum 3-7 days then the 7 days is for high dose biotin, the amount you get in a B Complex is usually around 400mcg which is a low dose so 3 days would be enough to leave it off.

[Pearlteapot in reply to SeasideSusie]

Perfect, thanks.

[userotc in reply to SeasideSusie]

Susie, does it also take ~4m (or less) for B Complex to effect B12 levels, in your experience? I think you may have also advised in the past on here so apologies if so.

[SeasideSusie Remembering in reply to userotc]

userotc

It's only to do with how much you hold on to not how long it takes to improve your level.

So say your B12 level is low and you need to supplement with a separate B12 (usually 1,000mcg or 5,000mcg) to improve your level and you've perhaps tested whilst taking it and your level is good, if you want to know if your body is maintaining that level without supplementation you'd leave it off for 4 months.

Ideally our store of B12 is good for about 2 years apparently but there are, of course, some who don't hang on to it.

[userotc in reply to SeasideSusie]

Susie. Thanks, I realise it was a different question to the one you'd answered - sorry for any confusion. After checking, I understand it takes just a few weeks to increase levels after supplementing eg link below. Dad has supplemented for 4m so can now retest. nhs.uk/medicines/cyanocobal....

[Lynneypin in reply to SeasideSusie]

That’s so helpful. Thanks.

[HappyHealthyGirl in reply to SeasideSusie]

This is such useful information from lovely SeasideSusie - I've saved the post. 😍