welche vitamine fehlen bei haarausfall — which blood markers matter?

Hair loss can be linked to nutrient deficiencies, but the knowledge base lacks direct data on this topic. Common blood markers include ferritin (iron stores), vitamin D, zinc, vitamin B12, and sometimes biotin. However, evidence for biotin supplementation in non-deficient individuals is weak. Consumer DNA tests claiming 'hair loss genes' (e.g., FADS1, APOA2) are not clinically validated for this purpose. Blood tests are more reliable: low ferritin (<30 ng/mL), low vitamin D, or thyroid dysfunction (TSH) can contribute. Never self-supplement without lab confirmation; excess biotin can interfere with lab assays. Evidence: mechanistic/practice. Caveat: see a doctor for proper diagnosis; consumer tests are not diagnostic.