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A single 10mg oral dose of biotin interferes with thyroid function tests

This simple and small scale study demonstrated that even a single dose of 10 milligrams of biotin is enough to push TSH down, and FT4 and FT3 up sufficiently to potentially cause misdiagnosis.

10 milligrams was chosen because it is commonly available dose of biotin as a supplement. Anyone could take that single dose and never suspect any impact. That could leave them undiagnosed, wrongly diagnosed or inappropriately dosed.

Currently trials of biotin for multiple sclerosis are ongoing which use 300 milligrams of a form of biotin (said to be highly concentrated). Goodness knows what impact that could have on TSH, FT4 and FT3 tests!

Also, though this study focussed on these three thyroid tests, several other blood tests are also believed to be susceptible to the impact of biotin.

Thankfully, leaving off biotin for 24 hours was sufficient to get these tests back to where they should be. It might take longer for those taking higher doses, or taking biotin over a longer period, to see the impact dissipate - but I don't know how long. Others have suggested a few days.

I wonder how many have had their blood tests affected by biotin supplements?

Thyroid. 2017 Jun 14. doi: 10.1089/thy.2016.0623. [Epub ahead of print]

A single 10mg oral dose of biotin interferes with thyroid function tests.

Biscolla RPM1, Chiamolera MI2, Kanashiro I3, Maciel RMB4, Vieira JGH5.

Author information

1 Grupo Fleury, 89577, Endocrinology, Sao Paulo, SP, Brazil ;

2 Grupo Fleury, 89577, Endocrinology, Sao Paulo, SP, Brazil ;

3 Grupo Fleury, 89577, Endocrinology, Sao Paulo, SP, Brazil ;

4 Grupo Fleury, 89577, Endocrinology, Sao Paulo, SP, Brazil ;

5 Grupo Fleury, 89577, Endocrinology, Sao Paulo, SP, Brazil ;


This letter reports a study with a single 10 mg oral dose of biotin in 19 health subjects. The acute use of biotin interferes with measurement of TSH, free T4 and T3, in a fashion similar to a hyperthyroid subject, and the changes are reversible 24 hours after the biotin ingestion.

PMID: 28614993

DOI: 10.1089/thy.2016.0623

Edited 12:23 18/06/217:

Just want to make it crystal clear, this biotin issue does not affect all versions of thyroid function tests. It is an issue with the test itself - not any impact on your actual levels.

Edited 19:22 22/06/2017:

Drug Discov Ther. 2016;10(6):338-339. doi: 10.5582/ddt.2016.01074.

Biotin treatment causing erroneous immunoassay results: A word of caution for clinicians.

Sulaiman RA1.

Author information


Department of Medical Genetics, King Faisal Specialist Hospital and Research center.


Biotin or vitamin B7 when ingested in high doses may cause immunoassay interference leading to false potentially misleading results. It is important that clinicians should always interpret laboratory results in the context of patient's clinical state as erroneous results may lead to misdiagnosis and injudicious treatment with adverse patient outcome.

PMID: 28090070

DOI: 10.5582/ddt.2016.01074

[Indexed for MEDLINE]

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11 Replies

Oh my goodness, just checked all my supplements and realised I'm taking 80 micrograms a day. A much tinier dose. But I do have some small discrepencies in my thyroid test results, I've suspected it might be due taking supplements.


Me too! 30mcg in a B complex I take.


There is no clarity on biotin requirement or dosing.

30 or 80 micrograms is so very, very much less than the 10,000 micrograms used in the paper it is quite possible it has no discernible effect. Especially as we might be getting an unknown amount from our gut bacteria.

I'd hope that the next step for researchers would be to establish a threshold below which there is no measurable effect on any blood tests.

Adolescents and adults—

30 to 100 mcg.

The NHS view is that up to 900 micrograms (0.9 milligrams) is a safe intake. However, I doubt that they are considering the impact of biotin on blood tests.

Biotin (vitamin B7)

Biotin is needed in very small amounts to help the body break down fat.

The bacteria that live naturally in your bowel are able to make biotin, so it's not clear if you need any additional biotin from the diet.

Biotin is also found in a wide range of foods, but only at very low levels.

What happens if I take too much biotin?

There's not enough evidence to know what the effects might be of taking high daily doses of biotin supplements.

What does the Department of Health advise?

You should be able to get all the biotin you need by eating a varied and balanced diet. If you take biotin supplements, don't take too much as this might be harmful.

Taking 0.9mg or less a day of biotin in supplements is unlikely to cause any harm.


Good it has been studied. At least some sort of back up and should be added to laboratory manual.


100% agree - should be added to all the information (preparing for blood tests, etc.). Urgently.

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Thanks Helvella for this information. Many do take Biotin and wouldn't be aware of the changes in blood.


Multi vitamin/mineral supplements are often criticized for not containing enough to be of much help, yet the Phoenix Nutrition product I was taking had 250 mcg of biotin, which they suggest to be five times the RDA.

My most recent flare coincided with a previous discussion of the biotin issue, and was luckily caught by a less frequent thyroid function test. I wish the advice from the Oxford Handbook of Clinical Medicine had been applied earlier in my life: "have a low threshold for measuring TSH (in yourself, your friends, and your patients)", and there was less palpable annoyance more recently from the phlebotomist...

On a lower dose and having ceased taking the supplement with biotin, my TSH had risen but was still below 1.0 so triggered a fT4 test, which had dropped from 16 to 12 pmol/L (range: 9 - 25 pmol/L). Since then, my TSH has climbed to 3.0, despite increased doses, and I'm annoyed that fT4 isn't tested. Also annoyed that I appear to have developed Hoffman's (or is it Hoffmann's?) syndrome with weakened and sometimes very painful hip flexors and compartment syndrome from enlarged calves.

Before treatment (and any thought of supplements, with or without biotin), there was a time that my TSH had dropped from 5.5 to 0.42 with fT4 being 12 and 14 respectively, over the course of six months. I don't know whether I was sick euthyroid with an infection when I had TSH = 0.42 and fT4 =14 or whether my autoimmune hypothyroidism is accompanied by central hypothyroidism. I feel I was hypo as a toddler and through primary school, and had the first of several flares at the age of 12, so maybe what became normal for me was above average production of T3 with lowish T4.

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Thank-you very much Helvella, a very interesting piece of information

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Thank you for bringing up this topic on Biotin . Stopping with extra Biotin supplementation 24-48 hours prior to labs is very helpful .

You might also consider stopping Iron supplements 5-7 days prior to labs .

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Very informative... .so many hypothroids take high doses of biotin to combat the hair loss we so often experience. (I took it for months in high dose and it did help)..moral is leave off it when a blood test is due.

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We still need some good evidence as to how long we have to stop taking biotin before a test in the more extreme cases - like high doses every day for weeks or months.

Thankfully the paper is clear that only a short time is needed after a single dose.

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