Drug interactions
Biotin + Levothyroxine
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Biotin does not alter levothyroxine pharmacokinetics, but it can significantly interfere with thyroid immunoassays (falsely low TSH and falsely high free T4/T3), risking inappropriate levothyroxine dose changes.
Mechanism of action
Assay interference: excess biotin disrupts streptavidin–biotin immunoassay systems used for thyroid function tests; not a true PK/PD interaction.
Clinical management
Ask about biotin use before thyroid labs; withhold biotin for at least 48–72 hours before testing (longer, e.g., 3–5 days, if high-dose ≥100 mg/day); consider biotin-independent assays; do not adjust levothyroxine based solely on discordant results if recent biotin use is suspected; repeat labs after biotin washout and correlate clinically.
Drug reference
References
- The FDA warns that biotin may interfere with lab tests: FDA Safety Communication (updated) — FDA
- Biotin interference with clinical immunoassays — UpToDate
- Biotin interference with thyroid function tests — American Thyroid Association
- Biotin: Drug information — Lexicomp
Frequently asked questions
Can I take Biotin with Levothyroxine?
The interaction is rated: Moderate. Biotin does not alter levothyroxine pharmacokinetics, but it can significantly interfere with thyroid immunoassays (falsely low TSH and falsely high free T4/T3), risking inappropriate levothyroxine dose changes.
How serious is the interaction between Biotin and Levothyroxine?
The interaction is rated: Moderate. Evidence level: High.
How is the interaction between Biotin and Levothyroxine managed?
Ask about biotin use before thyroid labs; withhold biotin for at least 48–72 hours before testing (longer, e.g., 3–5 days, if high-dose ≥100 mg/day); consider biotin-independent assays; do not adjust levothyroxine based solely on discordant results if recent biotin use is suspected; repeat labs after biotin washout and correlate clinically.
Why do Biotin and Levothyroxine interact?
Assay interference: excess biotin disrupts streptavidin–biotin immunoassay systems used for thyroid function tests; not a true PK/PD interaction.
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