How are MTHFR and Müdigkeit related?

The link between MTHFR variants (e.g., C677T) and fatigue is often overstated in direct-to-consumer marketing and online forums. Evidence from observational studies suggests a modest association: certain MTHFR polymorphisms can lead to mildly elevated homocysteine, which has been linked to fatigue in some populations. However, the effect size is small, and causality is not firmly established (evidence grade: human-moderate). Fatigue is multifactorial – sleep, stress, nutrition, thyroid function, and mental health are far more common contributors. A consumer DNA result for MTHFR does not diagnose a condition or predict fatigue reliably. In Germany, the Genetic Diagnostics Act (GenDG) restricts such tests for medical purposes; MyBody-X tests are lifestyle-oriented and not diagnostic. Self-supplementing with high-dose folate without medical supervision can be harmful (e.g., masking vitamin B12 deficiency). Practical takeaway: MTHFR may be one piece of a complex puzzle, but it should not be the primary focus when addressing fatigue.