Off B12 a week before B12 blood test or not?

[Pinkpetite]

Hello, my mum is due a repeat B12 blood test (and hoping for a full iron panel too which I have just requested) - does she need to stop the B12 supplements a week before the blood test? Or is stopping B vitamins only necessary before the thyroid blood tests? Many thanks.

[SeasideSusie Remembering]

Pinkpetite

does she need to stop the B12 supplements a week before the blood test? Or is stopping B vitamins only necessary before the thyroid blood tests?

This is the answer I received from Medichecks when I queried this:

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.

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.

Biotin covers stand alone biotin supplements or biotin contained in B Complex, hair/nail supplements, etc.

So if she takes a B Complex containing a relatively small amount of biotin, eg 400-500mcg, then leave off for about 3 days. If a higher strength biotin supplement, eg 5mg or 10mg, leave off for 7 days.

If she wants to see what level her B12 supplement is achieving then continue taking up to and including the day before the test which is what I have read elsewhere and disagrees with Medichecks saying to leave off for one week.

[Pinkpetite in reply to SeasideSusie]

OK thanks, my mum is not on a B complex yet as I'm adding one thing at a time. I'll tell her to stop the B12 the day before 😊