welche nährstoffe fehlen bei haarausfall — which blood markers matter?

The question of which nutrient deficiencies cause hair loss is common, but the answer depends on the individual cause. The provided context documents contain no specific information on hair loss or relevant blood markers. In general medical practice, iron (ferritin), zinc, vitamin D, vitamin B12, and selenium are considered relevant – but only if an actual deficiency exists. A ferritin level below 30–40 ng/mL is often associated with diffuse hair loss, as is low vitamin D (<30 nmol/L). Blood markers such as TSH, sex hormones (e.g., DHEA-S, testosterone), and thyroid parameters can also provide clues. Importantly, nutrient deficiency is not the only cause; genetics, stress, hormonal changes, and inflammation often play a larger role. Many direct-to-consumer tests promise simple analysis, but the evidence for the predictive power of individual genes (e.g., FADS2, MTHFR) is weak to mechanistic. Blood markers are more informative than genetic tests, but they must be interpreted in the overall context. Without medical evaluation, supplementation can even be harmful (e.g., too much selenium). Therefore, for persistent hair loss, a doctor visit with a complete blood count, ferritin, vitamin D, zinc, and thyroid values is advisable. The evidence for individual 'hair nutrients' is often overrated.