welche blutwerte bei müdigkeit und erschöpfung — what are common causes?

For fatigue and exhaustion, the most common blood tests ordered in clinical practice include: complete blood count (hemoglobin, MCV) to rule out anemia, ferritin (iron stores), vitamin B12, folate, vitamin D, thyroid function (TSH, fT3, fT4), fasting glucose or HbA1c, inflammatory markers (CRP), and liver/kidney function. Electrolytes (e.g., magnesium) and iron status (transferrin saturation) may also be relevant. Importantly, many causes of fatigue are not detectable by blood tests alone – psychological stress, sleep deprivation, lack of exercise, or chronic stress often play a larger role. The evidence for these lab parameters varies: strong (human-strong) for iron deficiency anemia and hypothyroidism, moderate (human-moderate) for vitamin D deficiency. Some tests (e.g., serum vitamin B12) have methodological limitations (e.g., falsely normal levels in functional deficiency). Consumer DNA tests (e.g., MTHFR) are not validated for fatigue workup and are not recommended by medical societies. Laboratory diagnostics should always be performed by a physician who interprets results in clinical context. Self-referral for lab tests without medical guidance can lead to misinterpretation and unnecessary costs.