welche blutwerte bei müdigkeit und erschöpfung — when to see a doctor?

For persistent fatigue and exhaustion, clinically established blood tests include a complete blood count (hemoglobin, MCV), ferritin (iron stores), vitamin B12, vitamin D, TSH (thyroid), fasting glucose, and electrolytes. A single blood cortisol measurement provides only a snapshot and cannot reliably assess HPA axis function; dynamic tests (e.g., diurnal salivary cortisol) are required. Evidence is strong for iron deficiency (Hb, ferritin), moderate for B12 and D (observational studies), and practice-based for cortisol. You should see a doctor if fatigue lasts more than two weeks, is unexplained, or is accompanied by weight loss, fever, night sweats, shortness of breath, or concentration difficulties. Caution: direct-to-consumer tests may give false reassurance or unnecessary worry; abnormal results should always be confirmed by a physician. The evidence level is mixed: some markers have robust clinical data, others rely on practice guidelines.