Iodine 131 radiation usually lasts about a month to two months, due to individual differences this time is not absolute, it is recommended to consult a doctor. Iodine 131 is an artificial radionuclide that is commonly used in the treatment of diseases such as hyperthyroidism or thyroid cancer. Iodine 131 releases beta rays during the decay process, and beta rays have a strong ionizing radiation ability, causing some of the thyroid follicular cells to degenerate and necrotic, reducing the synthesis and secretion of thyroid hormones, and shrinking the size of the thyroid gland, thus achieving the purpose of treating hyperthyroidism. The effective half-life of iodine 131 in the thyroid gland is about 35-45 days, and the duration of action of a single therapeutic dose on the thyroid gland can be up to 30-60 days or even longer. Avoid close and prolonged contact with other people (within 1 meter, more than 3 hours) for 1 week after iodine 131 treatment. Avoid close contact with infants, young children and pregnant women for 2 weeks after treatment, and avoid sharing tableware with others. If there is any discomfort, you should be instructed by a doctor to standardize the treatment, and the doctor should formulate an individualized diagnosis and treatment plan according to the specific condition, so as to avoid delaying the condition.