Most adults need 30 mcg of biotin per day, and the easiest way to get it is through everyday foods like eggs, nuts, and seeds. True biotin deficiency is uncommon in people eating a varied diet, but certain medications, genetic conditions, and dietary patterns can lower your levels. Here’s what to know about food sources, supplements, and the factors that affect how much biotin your body actually uses.
Best Food Sources of Biotin
Biotin is found in a wide range of foods, though the amounts per serving tend to be small. Animal products are generally the richest sources. Organ meats, particularly liver, contain the highest concentrations of any food. Cooked eggs are another reliable source (cooking matters, which we’ll get to below). Salmon and dairy products also contribute meaningful amounts.
If you eat a plant-based diet, you can still meet your needs. Sunflower seeds provide about 9% of your daily value in a quarter cup. A half cup of cooked sweet potato delivers around 8%, and a quarter cup of almonds covers about 5%. Legumes, whole grains, and bananas also contain smaller amounts. The key for vegans and vegetarians is variety: no single plant food is packed with biotin, but a mix of nuts, seeds, legumes, and vegetables adds up over the course of a day.
How Much You Need by Age
There’s no formal Recommended Dietary Allowance for biotin because the research wasn’t strong enough to set one. Instead, the NIH established Adequate Intakes, which are best estimates based on what healthy populations typically consume.
- Infants (0–12 months): 5–6 mcg
- Children (1–8 years): 8–12 mcg
- Tweens and teens (9–18 years): 20–25 mcg
- Adults 19 and older: 30 mcg
- Pregnant women: 30 mcg
- Breastfeeding women: 35 mcg
These numbers are easy to reach through diet alone. A single serving of liver can exceed your daily target many times over, and a combination of eggs, nuts, and whole grains throughout the day will generally cover it without any thought.
Your Gut Bacteria Make Biotin Too
Your intestinal bacteria produce some biotin on their own. This is a bonus source beyond what you eat, though researchers still aren’t sure exactly how much of this bacteria-produced biotin your body actually absorbs and uses. One practical takeaway: long-term use of antibiotics, particularly sulfonamide (sulfa) drugs, can reduce this bacterial production. If you’ve been on extended antibiotic courses, your total biotin supply may dip.
Why Raw Eggs Block Biotin Absorption
Raw egg whites contain a protein called avidin that binds to biotin with extraordinary strength. It’s actually the strongest non-covalent bond found in nature. When avidin latches onto biotin, the complex resists digestion entirely, so the biotin passes through your gut without being absorbed.
In practical terms, a single raw egg is unlikely to cause problems. The biotin-binding capacity of the white roughly cancels out the biotin content of the yolk, so you essentially break even. But regularly consuming large quantities of raw egg whites, such as in smoothies or bodybuilding shakes, could tip the balance toward depletion over time. Cooking denatures avidin and eliminates the issue completely.
Medications That Lower Biotin Levels
Several common medications interfere with biotin in different ways. Long-term use of certain anti-seizure drugs, including phenytoin, carbamazepine, and primidone, can reduce blood biotin levels. These drugs appear to block biotin absorption in the gut, reduce the kidneys’ ability to reclaim biotin before it’s excreted, and speed up how quickly the body breaks biotin down. Valproic acid, another seizure medication used in children, has been linked to hair loss that reversed with biotin supplementation.
If you take any of these medications long-term, your biotin needs may be higher than the standard 30 mcg. This is worth discussing with whoever manages your prescription.
Biotinidase Deficiency: A Genetic Factor
Some people are born with a condition called biotinidase deficiency that prevents the body from recycling biotin normally. Biotin in food is bound to proteins, and an enzyme called biotinidase is responsible for freeing it so your body can use it. Mutations in the BTD gene reduce or eliminate this enzyme’s activity.
Profound biotinidase deficiency means the enzyme works at less than 10% of its normal capacity. Partial deficiency means it works at 10% to 30%. Without enough free biotin circulating, the enzymes that depend on it to break down fats, proteins, and carbohydrates can’t function properly, leading to a buildup of toxic byproducts. Symptoms can include skin rashes, neurological problems, and hair changes. This condition is typically caught through newborn screening and managed with lifelong biotin supplementation at higher doses than what food alone provides.
Do Biotin Supplements Help Hair and Nails?
This is the main reason most people search for biotin, and the evidence is disappointing. A systematic review of biotin supplementation for hair loss found that biotin taken alone did not consistently improve hair growth in controlled studies. In one small randomized trial of healthy men, 5 mg of biotin per day (over 160 times the adequate intake) did nothing for hair growth rate, while minoxidil did. Adding biotin to minoxidil didn’t improve results beyond what minoxidil achieved on its own.
When studies did report improvements, they typically involved combination products containing multiple ingredients, making it impossible to credit biotin specifically. Researchers also found mixed results when measuring biotin levels in people with hair loss compared to those without. Some studies found lower levels in hair loss patients, others found no difference.
The bottom line from current evidence: if you’re genuinely biotin-deficient, supplementation can reverse hair and skin symptoms caused by that deficiency. But if your levels are normal, extra biotin is unlikely to make your hair grow faster or your nails stronger. Clinically meaningful deficiency is uncommon in anyone eating a balanced diet.
One Risk of High-Dose Supplements
Biotin supplements are water-soluble and generally considered safe, but they create a hidden problem: interference with common blood tests. Biotin is used as a reagent in many lab assays, and high circulating levels of the vitamin can skew results for thyroid hormones, troponin (used to diagnose heart attacks), and other critical tests. Biotin clears the body relatively quickly, with a half-life of about two hours. At doses of 5 to 10 mg per day, levels typically drop fast enough to avoid interference with modern tests. But at the mega-doses sometimes marketed for hair growth (100 to 300 mg per day), the risk becomes real.
If you take biotin supplements and have upcoming blood work, mention it to your provider. Stopping supplements for 24 to 48 hours before a blood draw is usually enough to clear the biotin from your system and avoid misleading results.
Choosing a Biotin Supplement
Most biotin supplements contain d-biotin, which is the naturally occurring and biologically active form. Supplements are available as standalone capsules, gummies, and as part of B-complex or multivitamin formulas. Doses on store shelves range wildly, from 30 mcg (matching the daily adequate intake) up to 10,000 mcg or more.
For someone eating a reasonably varied diet, supplementation is unnecessary. If you do choose to supplement because of a medication interaction, a restrictive diet, or a confirmed deficiency, a dose in the range of 30 to 100 mcg is more than sufficient for most people. The mega-dose products (2,500 to 10,000 mcg) marketed for beauty benefits lack strong clinical support and increase the risk of lab test interference without proven upside.