welche vitamine bei müdigkeit — which blood markers matter?

Fatigue can stem from many causes, but certain blood markers are especially relevant. Low ferritin (iron deficiency) is a common cause, particularly in women. Vitamin B12 and folate should also be checked, as deficiencies can lead to anemia and exhaustion. Vitamin D deficiency is associated with fatigue, though evidence for a causal role is moderate – many observational studies show links, but randomized trials are inconsistent. Thyroid function (TSH) is important because hypothyroidism causes fatigue. A complete blood count can reveal anemia or infection. Important: DNA tests for MTHFR variants (like rs1801133) are not suitable for diagnosing vitamin deficiencies; they only indicate small-effect genetic predispositions. Clinical blood testing remains the gold standard. For persistent fatigue, a doctor should interpret results, as other causes (sleep, stress, thyroid) may be involved. Evidence: human-moderate. Sources: EFSA on vitamin D and iron; clinical guidelines for fatigue workup.