Does Biotin (high-dose, >5000mcg) interact with Levothyroxine?

Supplement · Considered, not recommended

Biotin (high-dose, >5000mcg) and medications.

Why it sits outside our recommendations, and what to consider instead.

Biotin (high-dose, >5000mcg) is not in the Distil recommendation database. We surface it here deliberately, because why a compound is left out is as useful as what we recommend.

The issue with high-dose biotin (above 5,000mcg) is not toxicity. Biotin itself is very safe. The problem is that at these doses it interferes with a wide range of laboratory blood tests that use biotin-streptavidin chemistry. Thyroid panels, troponin (the heart-attack marker), vitamin D, and several hormone and pregnancy tests can all read falsely high or falsely low. The FDA issued a safety communication on this in 2017 after a patient died following a falsely low troponin result.

The hair-and-nail benefit only shows up in people who are genuinely biotin-deficient, which is rare. So the everyday megadose carries a real downside, wrong test results, for a benefit most people will not get. An ordinary B-complex covers your biotin needs without the assay interference.

What to consider instead. Every option below is in the Distil database, so you can check each against your own medications:

Vitamin B Complex: an ordinary dose covers biotin without the high-dose assay problem
Collagen Peptides: modest evidence for skin elasticity; mixed and mostly industry-funded
Silica: sometimes used for hair and nails; check iron and zinc first if there is real shedding

We still hold the documented interactions for Biotin (high-dose, >5000mcg), which is why it stays in the interactions checker even though we do not recommend it. Below are the 1 documented pair we have explicitly assessed: 1 amber. Every call is cited to a clinical reference (PMID) or the British National Formulary.

Documented interactions

Last reviewed 8 June 2026. Each interaction below is assessed against PubMed-indexed evidence.

Blood-test (assay) interference

Amber Does interact with Levothyroxine?

High-dose biotin (the amounts in many hair, skin and nail supplements) does not change how levothyroxine works, but it can make your thyroid blood tests read wrong. It can push free T4 and free T3 falsely high and TSH falsely low, which can look like an overactive thyroid that is not really there, or hide a result your GP needs to see to set your dose. Because people on levothyroxine have their thyroid checked regularly, it is sensible to pause high-dose biotin for two to three days before any thyroid blood test, and to tell whoever takes the blood that you have been taking it.

Evidence: Well established across multiple human studies or interaction references.

PMID 27362288 · PMID 29982406 · PMID 32118725 · PMID 28534685 · PMID 29856977 · BNF: Levothyroxine

What this page does not say. Leaving a compound out of our recommendations is not a verdict that it is useless for everyone. It is a statement about safety, evidence, or interaction load in the context Distil screens for. Discuss any supplement decision with whoever manages your prescriptions.

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For adults over 18. This tool gives evidence-graded information, not medical advice. Always discuss changes with your GP or pharmacist, especially if you take any medication, are pregnant, breastfeeding, or have a serious health condition.

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