Biotin (Vitamin B7)
The beauty vitamin for hair, skin, and nails — but the science is more nuanced than the marketing
Also known as: Vitamin B7 • Vitamin H • Coenzyme R
Overview
Biotin (vitamin B7) is a water-soluble B vitamin that serves as a coenzyme for five carboxylase enzymes involved in fatty acid synthesis, amino acid metabolism, and gluconeogenesis. It became the darling of the beauty supplement industry due to its role in keratin production — the structural protein in hair, skin, and nails. However, the evidence for biotin supplementation in people without deficiency is surprisingly thin. True biotin deficiency is rare in developed countries because gut bacteria produce biotin and it's found in many foods. The most compelling use case is for individuals with biotinidase deficiency, those on certain medications (anticonvulsants, isotretinoin), or pregnant women. An important safety note: high-dose biotin (5,000-10,000 mcg) can interfere with laboratory tests, causing falsely elevated or decreased results for thyroid function, troponin (heart attack marker), and other critical tests.
Key Benefits
Hair Growth & Keratin Production
Biotin is a cofactor for carboxylases involved in keratin synthesis. In individuals with biotin deficiency, supplementation clearly improves hair growth and reduces hair loss. However, for people with adequate biotin status, the evidence for additional hair growth benefits is limited to anecdotal reports and small, uncontrolled studies.
Nail Strength
The strongest evidence for biotin supplementation in non-deficient individuals comes from nail studies. A Swiss study found that 2,500 mcg daily for 6 months increased nail thickness by 25% in women with brittle nails. This is likely because nails have a higher keratin turnover rate than hair.
Skin Health
Biotin deficiency causes characteristic skin symptoms including seborrheic dermatitis, eczema, and skin rashes. Supplementation resolves these symptoms in deficient individuals. For those with adequate biotin, supplementation may support skin barrier function through its role in fatty acid synthesis.
Blood Sugar Metabolism
Biotin plays a role in gluconeogenesis and may improve glucose metabolism. Some studies show that high-dose biotin (8,000-16,000 mcg) combined with chromium picolinate can improve glycemic control in type 2 diabetes. This is an emerging research area.
Dosage & How to Take
The Adequate Intake (AI) for biotin is 30 mcg/day for adults. Beauty supplements typically provide 2,500-10,000 mcg — 83x to 333x the AI. There is no established Upper Limit because toxicity is extremely rare, but high doses interfere with lab tests.
| Purpose | Dose | Notes |
|---|---|---|
| General health | 30-100 mcg/day | Easily obtained from diet |
| Hair and nail support | 2,500-5,000 mcg/day | Most common beauty supplement dose |
| Brittle nails (studied dose) | 2,500 mcg/day for 6+ months | Based on Swiss nail thickness study |
| Blood sugar support | 8,000-16,000 mcg/day | High dose, under medical supervision |
Best Time to Take
Can be taken any time of day. No strong evidence for timing preference. Some people take it with breakfast for consistency.
With or Without Food
Better absorbed with food, though biotin is well-absorbed regardless. Taking with a meal reduces the chance of stomach upset.
Forms & Bioavailability
| Form | Absorption | Best For | Notes |
|---|---|---|---|
| D-Biotin (Standard) | High | General supplementation | The biologically active form used in all quality supplements. |
| Biotin Gummies | High | Taste preference | Popular format but contains added sugars. Same bioavailability as capsules. |
| Biotin + Collagen Combos | High | Comprehensive beauty support | Combines keratin support (biotin) with structural protein (collagen). |
Side Effects & Safety
Common
- Acne breakouts (especially at high doses)
- Skin rashes in sensitive individuals
Rare
- Digestive upset
- Insomnia at very high doses
Contraindications
- CRITICAL: Inform your doctor about biotin supplementation before any blood tests — high-dose biotin causes false results for thyroid, troponin, and other lab values
- May interact with anticonvulsant medications
Interactions
High-dose biotin (>5,000 mcg) interferes with immunoassays, causing false thyroid results, false troponin results, and other lab errors
These medications deplete biotin levels; supplementation may be beneficial
Avidin in raw egg whites binds biotin and prevents absorption
May deplete biotin; supplementation may help with hair loss side effect
Scientific Research
Biotin for Brittle Nails
2,500 mcg daily for 6 months increased nail thickness by 25% in women with brittle nails
Biotin Interference with Lab Tests
FDA issued a safety communication warning that biotin supplementation can cause clinically significant errors in laboratory tests
Biotin and Hair Loss
Systematic review found insufficient evidence to recommend biotin for hair loss in individuals without biotin deficiency
Food Sources
Frequently Asked Questions
Medical Disclaimer
This content is for educational and informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional before starting any supplement regimen, especially if you have pre-existing health conditions or are taking medications. The statements on this page have not been evaluated by the Food and Drug Administration.