Biotin (vitamin B7) deficiency is very rare in healthy people because biotin is widely available in food and produced by gut bacteria. When deficiency does occur, it's typically caused by specific medical conditions, certain medications, or excessive consumption of raw egg whites (which contain avidin, a biotin-binding protein).
Common symptoms
Hair thinning or hair loss
Brittle, splitting nails
Scaly red rash, especially around the eyes, nose, and mouth
People consuming large amounts of raw egg whites regularly (avidin binds biotin)
People taking long-term anticonvulsants (carbamazepine, phenobarbital, phenytoin, primidone)
People on long-term antibiotic therapy (alters gut bacteria)
People on long-term parenteral nutrition without biotin supplementation
Newborns with genetic biotinidase deficiency (screened for at birth in most US states)
Pregnant women (marginal biotin status is somewhat common in pregnancy)
People with severe malabsorption conditions
When to see a doctorHair loss has many more common causes than biotin deficiency (iron deficiency, thyroid issues, hormonal changes). True biotin deficiency rarely causes hair issues without other symptoms. CRITICAL WARNING: high-dose biotin supplements (≥5 mg/day, common in 'hair, skin, nails' products) cause SIGNIFICANT INTERFERENCE with many lab tests — including troponin (heart attack), TSH (thyroid), hCG, and others. Stop biotin at least 72 hours before lab work, and tell your doctor if you take it.