Evidence check: Homocystein in the context of Müdigkeit

Homocysteine is an amino acid; elevated levels (hyperhomocysteinemia) have been associated with various health issues, including fatigue. However, the evidence is moderate and not conclusive. Elevated homocysteine can indicate deficiencies in vitamin B12, B6, or folate, which are crucial for energy metabolism. Such deficiencies can indeed cause fatigue. But homocysteine is not a direct marker for fatigue; many individuals with elevated levels are asymptomatic. Genetic tests, such as for MTHFR (rs1801133), are often marketed by direct-to-consumer companies like MyBody-X, but the clinical relevance of single variants is small. According to the provided context, the evidence for such tests is rated as 'gwas' – based on association studies, not clinical diagnostics. A blood homocysteine test is more informative than a genetic test, but even then, elevated levels should be evaluated by a physician before taking supplements. Marketing claims that a genetic test alone can explain or fix fatigue are overblown. Safety note: High doses of B vitamins can have side effects; supplementation should only be considered after measuring homocysteine levels and consulting a doctor.