Myth: Biotin is an effective hair growth supplement.

Biotin for Hair Growth: Miracle Supplement or Marketing Hype?

Biotin has long been marketed as a go-to supplement for hair, skin, and nail health, with countless products boasting its ability to strengthen hair strands and promote growth. But does the research support the hype, or is this just another wellness trend built on marketing rather than evidence?

What is Biotin, and How is it Supposed to Work?

Biotin, also known as Vitamin B7, plays a key role in fatty acid metabolism, amino acid catabolism, and cellular growth. Since keratin (the protein in hair and nails) relies on these biochemical processes, the idea that biotin supplementation could enhance hair growth is biologically plausible. However, a mechanistic link between biotin and follicle proliferation remains weak.

While some animal studies suggest that biotin deficiency impairs follicle viability and DNA synthesis (Tahmasbi et al., 1998), this does not necessarily translate to enhanced hair growth in biotin-replete individuals.

What Does the Research Say?

Despite its popularity, research on biotin’s role in hair growth is inconclusive. Some studies suggest it may be beneficial under specific conditions, while others argue that its widespread use is not supported by strong evidence.

On the skeptical side, a review by Yelich et al. (2024) found little clinical evidence supporting biotin’s effectiveness for hair growth, highlighting only three relevant studies, none of which showed compelling results in healthy individuals. Similarly, Drake et al. (2023) found no strong evidence for biotin monotherapy in treating alopecia, instead noting that biotin is often part of multi-ingredient supplements, making its specific role difficult to isolate.

A systematic review by Soleymani et al. (2017) also found no proof that biotin enhances keratin production or hair follicle proliferation, suggesting that its effects may be largely anecdotal rather than scientifically proven. Further, a 1996 in vitro study by Limat et al. concluded that biotin did not enhance human follicular keratinocyte proliferation or keratin expression, even at pharmacological doses. This indicates that, at least in controlled environments, biotin does not significantly contribute to hair follicle activity.

However, some studies suggest biotin may be beneficial for individuals with underlying deficiencies or specific conditions. Patel et al. (2017) documented 18 case reports where biotin supplementation helped individuals with brittle nail syndrome, uncombable hair syndrome, and other biotin-deficiency-related conditions. Sabry et al. (2021) found that biotin supplementation benefited patients with telogen effluvium -- a temporary hair shedding caused by physical stress or illness -- only when they had low biotin levels, whereas those with normal biotin levels showed no significant improvement.

Anecdotally, many patients I have personally seen attest to subjectively experiencing improved hair and nail growth with biotin-containing supplements. Ablon and Kogan (2018) found that Nutrafol®, a multi-ingredient supplement containing biotin, improved hair growth in women with self-perceived thinning. But because biotin was just one of many active ingredients, its precise contribution remains unclear.

The Hidden Risk: Biotin Can Interfere With Lab Tests

One uncommon but noteworthy side effect of biotin supplementation is its impact on laboratory tests. Certain medical tests rely on a chemical reaction, biotin-streptavidin binding, which can be interrupted by excess biotin in the bloodstream, disrupting accurate results.

Biotin’s interference is particularly evident in thyroid function tests, where its presence can artificially lower TSH levels, leading to a false diagnosis of hyperthyroidism (Odhaib et al., 2019). Doses as low as 10 mg per day can significantly skew thyroid hormone test results. Fortunately, the effect does not actually lower your actual TSH, just the lab value that results when tested, and is quickly reversible: TSH levels will test accurately within 24-48 hours of stopping biotin, so knowledge of this effect can prevent misinterpretation of TSH lab tests.

Cardiac markers like troponin levels that are crucial for diagnosing heart attacks can also be impacted by biotin interference, and could have life-threatening implications. Similar to thyroid tests, 10 mg/day of biotin significantly interfered with high-sensitivity cardiac troponin T assays, causing falsely low troponin readings (Frame et al., 2019). This could lead to misdiagnoses or delayed treatment for myocardial infarction.

It's important to note that normal doses of biotin supplementation to prevent deficiency are around 30mcg per day (nih.gov). This is a small fraction of the amount typically contained in supplements marketed for hair growth, which often contain 2,500 to 10,000 mcg (2.5 to10 mg)—doses well beyond normal dietary intake. These high levels are precisely the ones that have been shown to affect medical test accuracy.

Groups At Risk for Biotin Deficiency/Inadequacy

• Individuals with biotinidase deficiency: Biotinidase deficiency is a rare genetic disorder that prevents the body from using biotin, leading to serious neurological and skin issues if untreated, but lifelong biotin supplementation can prevent symptoms.

• Individuals with chronic alcohol exposure: Chronic alcohol consumption impairs biotin absorption, leading to low plasma biotin levels in some individuals.

• Pregnant and breastfeeding women: Many pregnant and lactating women experience marginal biotin deficiency despite adequate intake, but the clinical significance remains unclear.

• People on restrictive diets that lack biotin: if you eat a special diet check if the common foods you eat are low in biotin.

Final Verdict: Should You Take Biotin for Hair Growth?

The current evidence suggests:

• If you are biotin-deficient, which is rare (nih.gov), supplementation can help hair regrowth.

• If you have normal biotin levels -- the case for almost everyone eating an average diet, which contains about 50mcg of biotin per day (nih.gov) -- there is no strong evidence that supplementation with biotin alone will improve hair growth.

• Some biotin-containing supplements may improve hair growth, but the contribution from biotin is unclear.

• High-dose biotin can interfere with medical tests, including thyroid function and cardiac troponin assays, which could lead to misdiagnoses.

Dr. Ryan M. Trowbridge, MD, MS, MA

Harvard-Trained Board-Certified Dermatologist and DermMythBuster

P.S. Have you come across any new or conflicting research on this topic? Please share—I’d love to explore it further with you!

Concerns about hair loss? If you’re worried about hair loss, consider consulting a professional for personalized advice.  You can obtain an online consultation from Dr. Trowbridge at Bridge Dermatology if you currently reside in California, Connecticut, Illinois, or Nebraska.

Citations

• Ablon G, Kogan S. A Six-Month, Randomized, Double-Blind, Placebo-Controlled Study Evaluating the Safety and Efficacy of a Nutraceutical Supplement for Promoting Hair Growth in Women With Self-Perceived Thinning Hair. J Drugs Dermatol. 2018;17(5):558-565.

• Drake L, Reyes-Hadsall S, Martinez J, Heinrich C, Huang K, Mostaghimi A. Evaluation of the Safety and Effectiveness of Nutritional Supplements for Treating Hair Loss: A Systematic Review. JAMA Dermatol. 2023;159(1):79-86. doi:10.1001/jamadermatol.2022.4867

• Frame, I., Joshi, P., Mwangi, C., Gunsolus, I., De Lemos, J., Das, S., Sarode, R., Balani, J., Apple, F., & Muthukumar, A. (2019). Susceptibility of Cardiac Troponin Assays to Biotin Interference. American Journal of Clinical Pathology, 151, 486–493. https://doi.org/10.1093/ajcp/aqy172.

• Obijiofor C, Akoh CC, Lo Sicco K. Nutritional Supplements and Hair Loss-Limitations to the Interpretation of Clinical Studies Before Implementation in Clinical Practice. JAMA Dermatol. 2023;159(8):891-892. doi:10.1001/jamadermatol.2023.1776

• Odhaib SA, Mansour AA, Haddad NS. How Biotin Induces Misleading Results in Thyroid Bioassays: Case Series. Cureus. 2019 May 23;11(5):e4727. doi: 10.7759/cureus.4727. PMID: 31363424; PMCID: PMC6663274.

• Office of Dietary Supplements. Biotin - Health Professional Fact Sheet. National Institutes of Health. Updated July 9, 2021. Accessed February 18, 2025. https://ods.od.nih.gov/factsheets/Biotin-HealthProfessional/

• Patel, D., Swink, S., & Castelo-Soccio, L. (2017). A Review of the Use of Biotin for Hair Loss. Skin Appendage Disorders, 3, 166 - 169. https://doi.org/10.1159/000462981.

• Sabry HH, Abd El Rahman SH, El Awady MA, Noureldine AM, Salama RA. Evaluation of serum level of biotin and effect of biotin replacement therapy in patients with telogen effluvium. Benha J Appl Sci. 2021;6(4 Pt 1):113-116. Available at: http://bjas.journals.ekb.eg.

• Soleymani T, Lo Sicco K, Shapiro J. The Infatuation With Biotin Supplementation: Is There Truth Behind Its Rising Popularity? A Comparative Analysis of Clinical Efficacy versus Social Popularity. J Drugs Dermatol. 2017;16(5):496-500.

• Tahmasbi, A., Galbraith, H., & Scaife, J. (1998). Effect of biotin on growth, viability and apparent DNA synthesis in cultured secondary hair follicles of the Angora goat. Proceedings of the British Society of Animal Science. https://doi.org/10.1017/s1752756200597907.

• Yelich A, Jenkins H, Holt S, Miller R. Biotin for Hair Loss: Teasing Out the Evidence. J Clin Aesthet Dermatol. 2024;17(8):56-61.