Is Biotin Safe with Levothyroxine?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Stop biotin supplements at least 48-72 hours before thyroid function tests (TSH, Free T4, Free T3). Inform your healthcare provider if you regularly take biotin, as it does not affect the actual drug but distorts monitoring labs.
Why this interaction occurs
High-dose biotin (≥5 mg/day) interferes with immunoassay-based thyroid function tests, causing falsely low TSH and falsely elevated Free T4 and T3 results, mimicking hyperthyroidism and potentially leading to inappropriate dose reductions.
Evidence
Evidence level: strong.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 302,514 reports mentioning Levothyroxine. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Levothyroxine + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Biotin interactions → · All Levothyroxine interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.