Thyroglobulin should be <1ng/ml in the TSH suppressed state on levothyroxine sodium tablets after total thyroidectomy, and <2ng/ml in the TSH stimulated state after 4 weeks off levothyroxine sodium or TSH. The thyroid gland is the sole source of thyroglobulin, and after total thyroidectomy there is usually no thyroid tissue remaining, so thyroglobulin (Tg) in the blood is usually low or undetectable. Lifelong levothyroxine sodium is also usually required after total thyroidectomy to prevent hypothyroidism and to act as a thyrotropin (TSH) suppressor. Generally, Tg should be <1ng/ml in TSH suppression therapy with levothyroxine sodium and <2ng/ml after discontinuing eugenol for 4 weeks or stimulating TSH. If Tg is ≥1ng/ml in the suppressed state or ≥2ng/ml in the stimulated state suggests that there may be residual thyroid tissue or recurrence of thyroid cancer, imaging or pathologic examination is needed to confirm the presence of recurrence or residual. Thyroglobulin should be rechecked every 3~6 months after thyroid cancer surgery, and it is recommended that patients follow the doctor's instructions for rechecking.