welche vitamine bei müdigkeit — when to see a doctor?

Fatigue can be a sign of vitamin deficiencies, especially vitamin D, B12, iron, or folate. However, self-supplementing with high doses is risky: the safe upper limit (UL) for vitamin D is 4000 IU/day, for vitamin B6 12 mg/day, and for iron 40 mg/day (adults). Higher doses can cause toxicity (e.g., B6 neuropathy, iron overload). DNA tests for vitamin needs are not validated for dosing. You should see a doctor if fatigue persists for more than two weeks, is accompanied by weight loss, fever, night sweats, or concentration problems, or does not improve with lifestyle changes. A simple blood test (including ferritin, vitamin D, B12) can identify the cause. Evidence for the ULs is strong (EFSA); the general fatigue workup is based on clinical practice. Sources: EFSA UL reassessments 2023–2024 (vitamin D, iron, B6).