Is IgG Unverträglichkeitstest useful for Müdigkeit?

IgG-based food intolerance tests are often marketed for fatigue, but the scientific evidence is weak. IgG antibodies to foods typically reflect normal immune exposure, not intolerance or allergy. Studies show these tests are not reproducible and yield many false positives. The German Society for Allergology and Clinical Immunology (DGAKI) advises against IgG testing for food intolerance. Fatigue has many potential causes—iron deficiency, sleep disorders, thyroid issues, etc. An IgG test can distract from proper medical workup and lead to unnecessary restrictive diets. Instead, persistent fatigue should be evaluated by a physician with blood tests for CBC, ferritin, vitamin D, B12, and thyroid function. Evidence: human-moderate (clinical guidelines and reviews).