welche blutwerte bei müdigkeit testen — when to see a doctor?

For persistent fatigue (lasting >2–4 weeks), seeing a doctor is advisable to rule out serious underlying conditions. Common blood tests include: complete blood count (hemoglobin, RBC) → anemia; ferritin → iron deficiency; vitamin B12 and folate → deficiencies; vitamin D → often suboptimal; TSH (thyroid-stimulating hormone) → thyroid function; inflammatory markers (CRP) → chronic inflammation; fasting glucose → diabetes; electrolytes (sodium, potassium, magnesium) → imbalances. Liver and kidney function may also be relevant. Evidence for these tests is good (human-observational, guideline-based). However, fatigue is a nonspecific symptom – not every lab value outside the normal range explains the fatigue. A self-test (e.g., MyBody-X VitalCheck Basic) can serve as a screening tool but does not replace medical diagnosis. If additional symptoms like weight loss, fever, night sweats, or shortness of breath occur, see a doctor immediately.