Evidence check: B12 in the context of Müdigkeit

Whether vitamin B12 helps with fatigue depends on the individual. B12 deficiency is a well-established cause of fatigue, weakness, and neurological symptoms (human-moderate evidence). However, deficiency is uncommon in the general population, especially among meat-eaters. Vegans, older adults, and people with gastrointestinal disorders (e.g., Crohn's disease, atrophic gastritis) are at higher risk. Blood tests (holotranscobalamin, methylmalonic acid) can reliably detect deficiency. In the absence of a confirmed deficiency, supplementing B12 for fatigue shows little to no benefit – evidence is weak (marketing/unclear). Many over-the-counter B12 products are marketed for 'energy' despite lack of efficacy in replete individuals. Caveat: chronically high B12 levels without deficiency may pose risks (e.g., acne, masking B12 deficiency anemia when taking folic acid). If you experience persistent fatigue, consult a doctor to check your B12 status before supplementing. MyBody-X tests can measure B12, but interpretation requires clinical context.