What do I need to stop taking before bloods tests?

[Tuxi1]

Not sure what to stop taking and when before thyroid and B12, D and folate tests. Biotin I gather but my other B's? and what about the T3 I am on - do i just continue with that? thanks

[SeasideSusie Remembering]

Tuxi1

When having thyroid tests it is advised to leave off biotin or B Complex for 3-7 days before the test. It is advised to have last dose of Levo 24 hours before the test. Last dose of T3 (or NDT) should be 8-12 hours before the test, splitting the dose into 2 or 3 the day before and adjusting time if necessary, taking last portion of dose 8-12 hours before test.

When having vitamin tests the following applies:

B12 - if you want to know your baseline level to know how much you are holding on to then you leave a B12 supplement off for 4-5 months. If you are taking B12 and want to know if your dose is adequate, too much or too little then you continue taking it up to and including the day before. On the day of the test take it after the blood draw.

Vit D - take up to and including the day before, on the day of the test take it after the blood draw.

Iron - when having any iron tests (including ferritin) iron supplement should be left off for 7 days and the test should be done after a 12 hour fast (water allowed).

[Tuxi1 in reply to SeasideSusie]

Thank you - I am surprised about the B12 - that is a long time off it to test.

[SeasideSusie Remembering in reply to Tuxi1]

I am surprised about the B12 - that is a long time off it to test

That's only for people who want to know what they are holding on to. As I said, if you want to know what level you are achieving with the dose you supplement with then you continue taking it, the result will tell you if you are taking too much, too little, or the right amount to maintain your level.

[shaws Administrator in reply to Tuxi1]

If our B12 is low we should expect the GP to do a test to exclude pernicious anaemia as it is another autoimmune condition. Once we have one diagnosed we can develop other conditions.

nhlbi.nih.gov/health-topics...