Vitamin E is a fat-soluble antioxidant that exists in several forms, with alpha-tocopherol being the most biologically active. This test measures vitamin E levels in the blood to evaluate antioxidant status and diagnose deficiency. Vitamin E protects cell membranes from oxidative damage by scavenging free radicals and preventing lipid peroxidation. Deficiency can cause peripheral neuropathy, ataxia, muscle weakness, and vision problems. Primary deficiency is rare and usually results from genetic disorders affecting vitamin E transport proteins. Secondary deficiency commonly occurs in conditions that impair fat absorption, such as cholestatic liver disease, cystic fibrosis, or short bowel syndrome. This test is essential for evaluating patients with unexplained neurological symptoms, monitoring nutritional status in malabsorption disorders, and assessing antioxidant capacity in various disease states.