Can IgG help with fatigue?

The question of whether IgG can help with fatigue lacks strong scientific support. IgG (immunoglobulin G) is an antibody involved in delayed immune responses. Some commercial IgG food sensitivity tests claim that certain foods trigger chronic fatigue via IgG-mediated reactions. However, the evidence is weak: systematic reviews find no consistent benefit of IgG-guided elimination diets for fatigue. Major medical organizations advise against using IgG tests for food intolerance diagnosis due to poor reproducibility and high false-positive rates. Fatigue has numerous potential causes—sleep disorders, iron deficiency, thyroid dysfunction, depression, and more. An IgG test does not replace a thorough medical workup. If you suffer from persistent fatigue, consult a physician to rule out underlying conditions. Dietary changes based on IgG results are often costly and unsupported by robust data. The evidence level is best described as 'marketing' or 'unclear'.