How Biotin Can Skew Your Thyroid Labs — and Lead to Misdiagnosis
By Dr. Alison DiBarto Goggin, Functional Medicine Physician
Little Black Bag Medicine | Virtual Functional Medicine Care
The Hidden Risk in Your “Hair, Skin, and Nails” Supplement
Many people take biotin (vitamin B7) daily to support hair, skin, and nail health but few realize it can distort lab results and lead to incorrect thyroid diagnoses.
In fact, I’ve seen patients who were prescribed thyroid medication or told they had a thyroid disorder when their bloodwork was simply being skewed by a common over-the-counter supplement.
How Biotin Alters Thyroid Blood Work
Most modern lab tests use a biotin–streptavidin binding system to measure hormones like TSH, free T4, and free T3. When you take high doses of biotin, this system becomes overloaded, creating false elevations or decreases in your lab results.
The issue is especially concerning because even a standard beauty dose (10,000 mcg or 10 mg) can cause changes significant enough to mimic thyroid disease.
What the studies show:
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TSH (Thyroid Stimulating Hormone): Falsely decreased
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Free T4 and Free T3: Falsely elevated
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Free T3 is the most susceptible to change
This lab pattern (low TSH, high T3/T4) is identical to hyperthyroidism, which can easily lead to an incorrect diagnosis or unnecessary treatment.
📚 Supporting research:
Study 1 | Study 2 | Study 3 | Study 4 | Study 5
More Than Thyroid: Other Tests Affected by Biotin
The thyroid isn’t the only system impacted. High-dose biotin can alter other hormone and nutrient results, including:
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Reproductive hormones: DHEA-S, estradiol, testosterone, progesterone, LH, FSH
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Nutrients: Vitamin D, Vitamin B12, ferritin
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Cardiac markers: Troponin I & T, Pro-BNP
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Proteins and enzymes: PSA, PTH, thyroglobulin, digoxin
Different lab analyzers and assay methods show different interferences, which makes standardizing recommendations challenging. But one fact remains clear: biotin changes the numbers.
How Long to Stop Biotin Before Blood Work
Research shows that biotin can start altering results within 2 hours of supplementing, and its effects may last up to 48 hours.
However, for patients with chronic illness, anemia, or nutrient deficiencies, I often recommend a longer washout period.
My functional medicine guidelines:
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Stop all supplements at least 48 hours before standard blood work.
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For nutrient or hormone testing, consider a 2–3 week break to see your true baseline.
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Always tell your provider which supplements you’re taking — even if they seem harmless.
My Professional Recommendation
At Little Black Bag Medicine, I help patients navigate these nuances every day. Accurate lab testing is the foundation of functional medicine and that starts with knowing what can interfere.
If your thyroid results don’t match your symptoms, or your medication doesn’t seem to be helping, it may be time to take a closer look at your supplement routine before adjusting your prescription.
The Bottom Line
Biotin is beneficial for beauty — but risky for accuracy.
Before your next blood draw, take a break, talk with your doctor, and make sure your test reflects your body, not your supplements.
✳️ Functional Medicine Support for Accurate Lab Testing
Understanding how your supplements, medications, and lifestyle choices affect your labs is key to healing — not guessing.
If you want personalized guidance to uncover the root causes of fatigue, hormone imbalance, or chronic symptoms, let’s work together through virtual consultations.
👉 Schedule Your Functional Medicine Consultation
(Includes a comprehensive review of your health history, lab interpretation, and personalized care plan.)
References
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Piketty ML, et al. Analytical interference of biotin on thyroid assays. Clin Chem Lab Med. PubMed 34042535
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Elston MS, et al. Biotin interference in thyroid function tests: A cautionary tale. J Clin Endocrinol Metab. PubMed 30221397
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Minkovsky A, et al. Biotin interference in immunoassays: Underrecognized and clinically significant. PubMed 32567529
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Plebani M, et al. Biotin interference in routine immunoassays: Laboratory and clinical considerations. PubMed 36889777
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Barbesino G. Misdiagnosis of Graves’ disease with biotin supplementation. PMC7478465