Biotin, or vitamin B8, is the most frequently cited vitamin in hair care formulas. It's listed in almost all "hair beauty" supplements sold in France. But what does it really do for the hair fiber, and when is supplementation beneficial? Here's what you need to know.
What is biotin (vitamin B8)?
Biotin is a water-soluble B vitamin, sometimes called vitamin H. It is produced in small amounts by the gut microbiota and must be obtained primarily through diet. Like all water-soluble vitamins, it is not stored in large quantities in the body and is eliminated in urine—making regular intake necessary.
Beyond its role in hair health, biotin contributes to the proper functioning of energy metabolism (lipids, proteins, carbohydrates), the maintenance of the nervous system, and the regulation of blood sugar. It also participates in the synthesis of other B vitamins, particularly B9 and B12.
The benefits of biotin on hair
The link between biotin and hair health is well established in the scientific literature, particularly in cases of deficiency. Here are the documented effects:
Stimulation of keratin production. Biotin is an essential cofactor for carboxylases, enzymes involved in the synthesis of the amino acids that make up keratin—the protein that constitutes 95% of hair. Without sufficient biotin intake, keratin production slows down, making hair thinner, more brittle, and dull. To better understand the role of keratin in hair structure, our article "Keratin and Hair: Role and Supplementation" provides a comprehensive overview.
Improved thickness and strength. A study published in the Journal of Clinical and Aesthetic Dermatology (2012) showed that biotin supplementation in women with significant hair loss and thinning reduced hair loss and improved hair thickness after 90 days. A 2017 systematic review confirms that biotin improves hair and nail growth in individuals with a known deficiency.
Reduction of seasonal hair loss. Biotin helps regulate seborrhea (excess sebum), which can clog follicles and hinder growth. It thus indirectly contributes to limiting hair loss associated with an unbalanced scalp.
Shine and vitality. By improving the structure of the cuticle (the outer protective layer of the hair), biotin helps maintain the natural shine and suppleness of the hair.
Scalp health. A biotin deficiency can cause rashes and scalp irritation. Appropriate supplementation helps maintain the balance of the skin's microenvironment.
What are the dietary sources of biotin?
Biotin is present in many common foods. The recommended daily intake (RDI) is 40 µg/day for an adult according to the EFSA.
The best food sources are brewer's yeast (one of the most concentrated), egg yolk (cooked — the avidin in raw egg white blocks the absorption of biotin), legumes (lentils, chickpeas, beans), oilseeds (almonds, hazelnuts, sunflower seeds), some vegetables (sweet potato, carrots) and some fruits (avocado, banana, tomato).
A varied and balanced diet generally covers biotin requirements. Supplementation is particularly useful in cases of significant dietary restriction, pregnancy or breastfeeding, long-term antibiotic use (which alters the intestinal flora that produces biotin), or identified signs of deficiency.
How to supplement with biotin?
Biotin supplements are available in capsule, tablet, or gummie form. Hair care formulas typically combine biotin with other synergistic nutrients: zinc (for keratin synthesis), selenium (a follicular antioxidant), vitamins B6, B9, B12, and vitamin E. This combination is more effective than biotin alone.
Blueberry-based formulas often enhance these combinations: its polyphenols improve scalp microcirculation and boost the effect of vitamins on hair growth. To choose the formula best suited to your needs, our article on hair growth supplements compares the main options available.
A 3-month treatment is recommended for visible and lasting results. The first effects (reduced breakage, improved shine) generally appear after 4 to 6 weeks.
Important note: High doses of biotin (5000 µg and above) can interfere with certain blood tests (thyroid, troponin, and hormone levels) by affecting immunological assays. Always inform your doctor if you are taking a biotin supplement before any blood test. Pregnant or breastfeeding women and children under 16 should seek medical advice before starting any supplementation.
Biotin supplementation is part of a comprehensive hair care routine. To maximize its effects, combine it with appropriate external treatments: scalp massages, weekly oil treatments, and sulfate-free hair products. Our article on how to care for your hair provides the foundation for an effective hair care routine, and our selection of the best plant-based oils for hair will help you complement your external treatments.
Frequently asked questions about biotin and hair
Does biotin make hair grow faster?
In cases of biotin deficiency, yes—supplementation can improve the speed and quality of hair growth. In a person without a deficiency, the effect on growth rate is more modest. However, biotin improves the thickness and strength of existing hair, reducing breakage and giving the impression of longer, thicker hair.
Is it possible to have too much biotin?
Biotin is water-soluble and eliminated in the urine—direct toxicity is very rare. However, very high doses (5000 µg and above) can interfere with certain laboratory tests. Follow the dosage recommendations on the chosen product and inform your doctor that you are taking biotin before having any blood tests.
How long do you need to take biotin to see results on your hair?
The first visible effects (increased shine, reduced breakage) generally appear after 4 to 6 weeks. For a significant impact on density and growth, a minimum 3-month treatment is necessary—as the hair renewal cycle is long, results cannot be assessed before this time.