Biotin & thyroid tests

Just to back up what others have posted about biotin affecting thyroid testing. I had a thyroid blood test done at GP unexpectedly and forgot that I should have stopped my supplements a few days before. I was just supplementing with Thornes b complex so not a high dose. The test came back and my levels had all suddenly normalised.

I asked for it to be redone as it was so anomalous and I had been supplementing. The test was redone about a week later and my TSH had shot up and my T4 down. I now have a diagnosis and medication!

Definitely stop supplementing biotin 4/5 days before any thyroid testing.

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9 Replies

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  • Your post will be helpful to quite a number of our members.

  • Yes. I was unexpectedly asked to do a blood test at an annual review. I refused on three grounds: it was afternoon, I had taken Levo that day and was taking B complex with biotin in. The surgery had no idea about biotin.

    If they make a fuss show them this article

    endocrinenews.endocrine.org...

  • Yes my GP today said she had never heard of it before (biotin). I had shown her the article and she was very receptive and interested.

  • Good for you for getting it rechecked, and then getting a diagnosis too :)

    I must admit that I now wonder about my first tests prior to diagnosis - not just thyroid but nutrient levels as well. I can't help but wonder if mine were actually lower than those in that first test result because I'd taken a multi vit/mineral up to the day before. Not that it matters now anyway, but I think there's a tendency with hypoT to try to join the 'very many' mysterious dots over the years prior to diagnosis!

    Hope you start to see an improve :)

  • Thank you! Am so pleased to be finally diagnosed. And I know what you mean about joining the dots. I have had symptoms for many years, and a miscarriage a few years ago...you can't help but wonder how long this has been affecting me for.

  • Hi. Thanks for sharing this. I was just about to post asking how long is it recommended to stop supplementing for before the test. I'm taking 10,000ug plus bcomplex but need to do thyroid checkups.

    It is interesting you've been on Thorne b as I was taking it during my last test, when my tsh was suppressed and ft4 above range. I knew of the possible biotin interference with ft4 but thought it was for high doses only (I did not stop taking the Thorne b beforehand). Do I understand what you say that your tsh was also affected? I believe info on here talked only about the ft4 reading on test and not biotin affecting the other tests or thyroid function.

    This would explain my conundrum of bloods indicating I'm close to being overdosed but me slipping back into hypo.

  • It depends on the lab and how they test but it can affect T4, T3 and TSH. See the article linked to by slowdragon above. The article only talks about high doses affecting the results but I was only taking thornes b complex and my TSH was lowered and my T4 raised. As it was an anomalous result I asked for it to be retested and TSH went up to 4.8 (from 3.18) and T4 down to 10.9 (from 13 something). Retest was done within two weeks. Interesting that it seemed to affect the result even at lower doses.

    My understanding is that it is recommended to stop taking it 4/5 days before testing. I now do this with all my supplements just in case.

  • Wow! That's a significant swing in your numbers. This may well explain my last results with tsh of 0.08 and ft4 of 22.5 whilst I'm nowhere near to feeling optimised. I've spent the last 3 months playing with doses, thinking I was close to being overmedicated so suspected some symptoms I was getting were from the dose being too high. Now I've been back to the same dose for 6 weeks and need to retest to see what's going on.

    Thank you very much for your help. Yet another example of how badly the condition is researched and understood and we are left to figure it out for ourselves.

    I know the relief you must be feeling, it took me over a decade to get diagnosed. Good luck with your recovery!

  • Thank you! 😊

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