How are IgG and fatigue related?

The relationship between IgG and fatigue is complex. IgG (immunoglobulin G) is a broad class of antibodies involved in many immune responses. Elevated IgG levels can indicate chronic infections, autoimmune diseases, or an overactive immune system, which may be associated with fatigue. However, IgG alone is not a specific marker for fatigue. Research links IgG mainly in the context of chronic inflammatory conditions (e.g., chronic infections, autoimmune diseases like lupus or rheumatoid arthritis). IgG-based food sensitivity tests are marketed for fatigue, but the scientific evidence for a causal link is weak and controversial. Most studies are small or show only correlations. IgG levels can be influenced by many factors (vaccinations, infections, medications). Therefore, a standalone IgG test is not recommended for fatigue evaluation. Your mention of low testosterone and B12 supplementation are separate factors that can also contribute to fatigue but are not directly linked to IgG. A comprehensive medical workup is advised.