Pernicious Anaemia Society
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Co factors blood test

I'll be going for my annual thyroid blood test (I was over active a few years ago) and will ask my gp to also test folate, ferritin, potassium (which was slightly below range last year) and vitamin D.

I supplement folate (or a vitamin B complex) and Vitamin D (in winter) on a daily basis. I eat as much potassium rich foods as I can and about once a week have a spatone iron supplement in a glass of orange juice.

I si weekly and mostly feel well on that

Should I continue taking the supplements as usual before the blood test or should I leave off for a few days or weeks?

Thank you

5 Replies

Maybe you could try posting this in thyroid group? Sorry I can't paste link on tablet, but it is a very active group with a lot of real experts.

Good luck

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link is

You can also search for other forums by selecting 'Browse Communities' from the 'My Communities menu on the header bar.

Like startagaingirl I would suggest posting on the Thyroid forum as the blood test is related specifically to a thyroid condition.

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Thanks for your replies. Sorry I wasn't very clear, I'm not really bothered about the the thyroid test as I feel that's working ok. It's 12 years since it was overactive and it seems to have behaved since then. The thyroid problem just gives me an excuse to have annual blood tests at my GP

Knowing that B12 tests are meaningless if you supplement I was just wondering about the other vitamin and iron supplements that I take. Will they skew the results of any folate, ferritin and vitamin D blood test that I'm going to ask for? Should I stop taking any or all of them before the test?

I'll be refusing a B12 test though!


I don't believe any others are skewed by supplementing, but again, the experts are in the thyroid group as many, many people there use these particular supplements xx


agreed - I think the mechanisms by which folate and vit d are transferred from blood to cell tend to be much less complex than those for B12.

folate isn't stored anywhere specific other than the amounts in your blood so relationship between amount ingested (including tablets) and amount in blood is going to be much simpler.

Ferritin is a protein that binds to iron so it can be used by the body - it's one measure for iron deficiency - but far from the only one as there are a few other things that can go wrong with iron.

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