Anti-thyroglobulin antibody is a blood test that measures the presence of antibodies against thyroglobulin, a protein found in the thyroid gland. This test is used to diagnose autoimmune thyroid diseases such as Hashimotos thyroiditis and Graves disease, as well as other thyroid-related conditions. The test is performed by taking a blood sample from the patient and analyzing it in a laboratory. Elevated levels of anti-thyroglobulin antibodies can indicate thyroid dysfunction and may require further evaluation and treatment.