Low thyroglobulin is most often seen in thyroid cancer patients whose serum thyroglobulin levels drop to very low or undetectable levels after successful surgical removal of thyroid tissue. Thyroglobulin is an iodinated glycoprotein in the thyroid gland, which is a storage form of iodine in the body within the thyroid gland, and the reference range of serum thyroglobulin is about 3 to 40 μg/L. The normal reference range for serum thyroglobulin is highly geographically specific because serum thyroglobulin concentrations are influenced by iodine intake. In areas of inadequate iodine intake, the mean thyroglobulin value and the upper thyroglobulin reference limit may be elevated in the population in relation to the degree of iodine deficiency. When low thyroglobulin is detected, prompt medical attention is required to identify the specific cause of the disease and to actively pursue standardized treatment under the guidance of a physician.