How Biotin Can Affect TSH (Thyroid Stimulating Hormone) Tests

Biotin, vitamin B7, is well known to cause falsely low TSH lab test results in many individuals


I just received my annual lab results. My T4 is normal but my TSH is quite high. I have been taking Biotin 2500 mg daily for about 6 months. I read that Biotin can affect the results of TSH levels. My MD is away for 2 weeks. Questions: 1) Could my results be incorrect as a result of the biotin? How long should I wait before I could get an accurate result after discontinuing the biotin? 2) I would prefer not to take a synthetic hormone treatment if my results are still elevated. Can you suggest an alternative?

Asked by Pat On Sep 26, 2018

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Sep 26, 2018

Biotin, also known as vitamin B7, vitamin H and co-enzyme R, is an essential water soluble vitamin, important for a variety of physiological processes in humans (1). Although dietary intake of biotin is generally sufficient for most individuals, it is a popular over the counter supplement, commonly used for:

  • Prenatal nutrition (2)
  • Hair loss (1, 3)
  • Brittle nails (3)
  • Neuropathy (4)
  • Muscle cramps (5)
  • Multiple sclerosis (6)

Biotin And Lab Tests

It has been well documented that biotin supplementation can interfere with several laboratory tests, not just tests involving the thyroid. Most studies note that small doses of biotin (~30 mcg) aren't likely to significantly affect lab values, but it is certainly a possibility with high doses (>30 mcg) (7, 8).

There are several theories as to why biotin can affect lab tests (i.e. TSH tests) (8, 9):

  • Biotin may block test assay signals, leading to falsely elevated test results.
  • Biotin may compete with biotin-containing complexes the test utilizes, which can lead to falsely low results.

Exactly which lab tests are potentially affected by biotin, and by what extent, isn't well known and evidence suggests that there may even be variability from test to test or with tests from different manufacturers.

In November 2017, the FDA released a safety communication warning about biotin supplementation and lab tests:

"Biotin in blood or other samples taken from patients who are ingesting high levels of biotin in dietary supplements can cause clinically significant incorrect lab test results.

The FDA has seen an increase in the number of reported adverse events, including one death, related to biotin interference with lab tests. Biotin in patient samples can cause falsely high or falsely low results, depending on the test. Incorrect test results may lead to inappropriate patient management or misdiagnosis. For example, a falsely low result for troponin, a clinically important biomarker to aid in the diagnosis of heart attacks, may lead to a missed diagnosis and potentially serious clinical implications."

Lab tests that are potentially affected by biotin supplementation are reported to include:

  • Beta human chorionic gonadotropin (beta–hCG)
  • Cortisol
  • Creatine kinase
  • DHEA-sulfate
  • Estradiol
  • Folate
  • Follicle stimulating hormone (FSH)
  • Insulin
  • Prostate specific antigen (PSA)
  • Thyroid stimulating hormone (TSH)
  • Thyroxine (T4)
  • Triiodothyronine (T3)

Biotin And TSH Testing

Several studies have investigated the effects of biotin supplementation of TSH testing specifically:

  • Biotin supplementation can falsely lower TSH levels in infants, young children and adults (10, 11). Doses as low as 10mg (10,000 mcg) per day have been reported to affect lab results.
  • In general, it is recommended to avoid taking biotin supplements for at least 8 hours prior to taking a thyroid stimulating hormone test to decrease the chance of altered results.
  • If you have been supplementing with biotin for an extended period of time, it may be necessary to stop it at least a few days prior to testing to avoid interference.


Final Words

Biotin can affect TSH lab test results, generally causing falsely low TSH levels. Most studies suggest not taking biotin supplements within 8 hours of a TSH test, but a longer discontinuation period may be necessary if you take biotin daily.

If your doctor recommends thyroid supplementation, the synthetic hormone (T4) is most common (e.g. Synthroid, levothyroxine, Levoxyl) but there are other "natural" options, such as desiccated thyroid (e.g. Armour Thyroid) which contains both T4 and T3. It is important to speak with your doctor regarding the best treatment options for your specific medical situation.

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