Eating non-iodized salt for three days may affect the thyroid function test. Thyroid function test can understand the level of thyroid hormones in the body, determine whether the indicators of the thyroid gland are normal or not, and help diagnose hyperthyroidism, hypothyroidism and other diseases. Eating non-iodized salt for three days before the thyroid function test may affect the results. Normal diet generally has no effect on thyroid function tests, but excessive eating needs to be avoided, especially blood should not be drawn after eating large amounts of sugary foods. Blood should be drawn in a quiet state, avoiding strenuous exercise and emotional stress. Patients who need to undergo thyroid function tests should actively cooperate with the healthcare personnel in the operation process, and it is recommended to go to the hospital for consultation when abnormal results occur.