Medichecks blood 🩸 test whilst on weekly B12 injections

[Kisca]

Hello 👋

I’ve just ordered my Medichecks advanced thyroid test .

I’ve held off biotin for this test but just read that I should also avoid B12 as well but I’m having weekly injections atm…..shall I do test anyway 🙈

Any advice much appreciated 🙏

[SeasideSusie Remembering]

Kisca

Medichecks have been inconsistent with the advice given about stopping supplements before testing.

A couple of years ago this is what they told one of our members who questioned their advice about biotin:

Because biotin is an ingredient used in many lab hormone test kits this can interfere with the measurement of thyroid hormones

It does this in an inconsistent way, causing falsely elevated results from some labs, and falsely low results from others. We recommend stopping biotin for one week prior to blood tests.

A little while later they altered their instructions to include information about leaving B12 off for one week but there was no information about leaving off biotin. I contacted them for clarification and they replied with the following:

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.

You are using B12 injections presumably because you have B12 deficiency, and your GP is giving them? If so then obiously you can't just stop them so continue them but do the injection after the blood draw on the day of the test.