Biotin, hair, skin and nails

Hair, skin and nail vitamins only help if you're deficient. The usual causes of hair loss: low iron (ferritin), vitamin D, too little protein, stress, thyroid and crash dieting.

• Test first: ferritin, vitamin D, TSH.
• Eat enough protein (1.2–1.6 g/kg) and calories.
• Biotin is rarely needed; note it skews blood tests (thyroid, troponin) — stop 2–3 days before a test.
• Collagen may help skin elasticity.

Heavy hair loss — see a dermatologist.