What should I stop before testing for Ferritin,... - Thyroid UK

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What should I stop before testing for Ferritin, Vit D, B12 and Folate

Pinkroses profile image

Hi. I started 125 Levo 3 months ago and my Thyroid test results now seem optimal (results shown below). I have been taking Vit D, B12, Iron and a multi vitamin since my last GP blood test showed these could be improved. I would like to have my Ferritin, Vit D, B12 and Folate tested and will have to go privately. What medication/supplements should I stop before taking the test? Also, are you aware of the cheapest test where I could get all 4 tested together. Medichecks have these in all different tests so it will cost quite a bit to get them all done. Thanks

TSH 0.06 (0.2 to 4.5), T4 18 (9 to 21) and T3 1.7 (0.9 to 2.4).

6 Replies
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I know you need to leave off iron supplements for around a week before testing. B12, for several months, so it's hardly worth testing it at all, once you've done your initial test before starting to supplement. I don't know about the other two, I'm sure someone else will be along who does know. :)

SeasideSusie profile image


As Jadzhia says, leave off iron for a week.

For a baseline of B12 you need to be off it for about 4 months. However, testing when supplementing can be useful, it shows that you are supplementing and gives an indication if you are taking enough or too much. I retest everything from time to time and the B12 result has helped me adjust the dose and I've found what keeps me stable around 1000.

You can continue with B12, B Complex and Vit D but just take them after you do your blood test that day.

The cheapest way to get vits and mins tested is with the thyroid/nutrient bundle from either Medichecks or Blue Horizon. Doing them individually would cost a fair bit more.



That is great. Thanks for your replies.

Don't take anything with biotin in (multi B's or multivitamins) for a couple of days before test as it can interfere with some lab tests causing false low TSH and false high ft3, ft4.🙂'

Oh boy I'm a numpty you're not testing them 😊 please ignore me lol

SeasideSusie profile image
SeasideSusieAdministrator in reply to fibrolinda

Oh yes! Sorry Pinkroses - major senior moment there! If your B Complex contains Biotin - B7 - then leave it off for 3-5 days as it can interfere with your results.

Thanks fibrolinda :)

Pinkroses profile image
Pinkroses in reply to fibrolinda

Thanks. The vitamin tests are combined with the thyroid results so I will stop my multi before the test as that contains biotin.

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