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Can biotin throw off thyroid and heart (troponin) blood tests?

Yes, at the high amounts sold in some supplements. The effect is documented in drug-level studies: when 6 healthy adults took 10 mg of biotin a day for a week, 9 of 23 lab tests built with biotin gave wrong results, some falsely high and some falsely low. Thyroid results can look like an overactive thyroid, and a falsely low troponin can hide a heart attack. Tell your doctor and the lab about any biotin before a blood test.

How well documented: Documented in drug-level studies. Studies in people measured the effect directly: the medicine’s blood levels or its effect, or a test result.

Last reviewed

How we grade evidenceEditorial policy

What's known

  • Drug-level studies. Six healthy adults took 10 mg of biotin a day for a week, and their blood was run on 37 test methods for 11 common lab measures, including the thyroid tests TSH, T4 and T3. Nine of the 23 tests that use biotin in their chemistry gave wrong results, and none of the 14 tests that don't. Some types read falsely high and others falsely low. ODS adds that even a single 10 mg dose has thrown off thyroid tests done within 24 hours. (Li 2017, ODS)
  • Case reports. A man with multiple sclerosis taking very high doses of biotin had results that looked like severe Graves' disease (an overactive thyroid), although he had no symptoms. The results became normal when he paused biotin. In another case, results normalized faster than real thyroid hormone can change, a sign that the test, not the thyroid, was wrong. (Barbesino 2016, Elston 2016)
  • Heart tests. The FDA warns that biotin can cause wrong results that may go unnoticed, keeps receiving reports of falsely low troponin (the blood test for a heart attack), and lists troponin tests still at risk. The FDA's 2019 safety notice reports that one patient taking high levels of biotin died after a troponin test gave a falsely low result, and NIH's ODS repeats it. A 2019 review counted 92 suspected cases reported to the FDA since 2016. In US emergency patients checked for a heart attack, though, high biotin levels were rare: 1 of 797 first samples, in a study with co-authors from the test's maker. (FDA, FDA 2019 notice, ODS, Bowen 2019, Mumma 2020)
  • On the levothyroxine label. The Synthroid label says biotin can make TSH, T4 and T3 results wrong. It tells prescribers to ask about biotin and to have patients pause it for at least 2 days before TSH or T4 tests. (Synthroid label)

What to do

  • Tell your doctor, and the person taking your blood, about any biotin you take, including multivitamins and B-complex products. A pharmacist can tell you whether a product contains it.
  • Before a thyroid test, the levothyroxine label's rule is a pause of at least 2 days. That rule covers TSH and T4 only. For other tests, ask your doctor or the lab what to do.
  • With chest pain or other heart attack signs, call emergency services at once and tell the team you take biotin, since it can make a troponin result falsely low.
  • If a prescriber recommended high-dose biotin for a medical condition, ask them before you pause it. Don't stop or change a prescribed medicine on your own.

Sources

  1. Li D, et al. Association of Biotin Ingestion With Performance of Hormone and Nonhormone Assays in Healthy Adults. JAMA. 2017. PubMed 28973622 · doi:10.1001/jama.2017.13705
  2. Barbesino G. Misdiagnosis of Graves' Disease with Apparent Severe Hyperthyroidism in a Patient Taking Biotin Megadoses. Thyroid. 2016. PubMed 27043844 · doi:10.1089/thy.2015.0664
  3. Elston MS, et al. Factitious Graves' Disease Due to Biotin Immunoassay Interference-A Case and Review of the Literature. J Clin Endocrinol Metab. 2016. PubMed 27362288 · doi:10.1210/jc.2016-1971
  4. US Food and Drug Administration. Biotin Interference with Troponin Lab Tests: Assays Subject to Biotin Interference. Content current as of 21 June 2022. FDA
  5. National Institutes of Health, Office of Dietary Supplements. Biotin: Fact Sheet for Health Professionals. Updated 10 January 2022. ODS
  6. US National Library of Medicine. Synthroid (levothyroxine sodium) tablets: prescribing information. DailyMed, revised 02/2024. DailyMed
  7. Mumma B, et al. Clinical risk assessment of biotin interference with a high-sensitivity cardiac troponin T assay. Clin Chem Lab Med. 2020. PubMed 32804676 · doi:10.1515/cclm-2019-0962
  8. Bowen R, et al. Best practices in mitigating the risk of biotin interference with laboratory testing. Clin Biochem. 2019. PubMed 31473202 · doi:10.1016/j.clinbiochem.2019.08.012
  9. US Food and Drug Administration. UPDATE: The FDA Warns that Biotin May Interfere with Lab Tests: FDA Safety Communication. Issued 5 November 2019 (archived copy; FDA's troponin page links to its own archive of it). FDA 2019 notice