1. A low iodine diet for 1-2 weeks prior to treatment puts the thyroid gland in a state of “iodine starvation”, which promotes more efficient uptake of therapeutic I-131 into the thyroid tissue. 2. It is recommended that all patients use “beta-adrenergic receptor blockers” such as propranolol, atenolol, metoprolol, etc. prior to treatment, unless they have contraindications to the use of such drugs. 3. If the patient has severe hyperthyroidism, such as very pronounced symptoms or thyroxine (FT4) levels that exceed 2 to 3 times the upper limit of normal, the patient should be pre-treated with antithyroid drugs (methimazole is preferred) for a period of time and discontinued 3 days prior to isotope therapy. 4. If the patient is combined with serious underlying pathology, such as heart disease, infection, liver failure, kidney failure, unwell-controlled diabetes, cerebrovascular disease, lung disease, etc., appropriate treatment must be given first, and then isotope therapy should be administered after the condition is stabilized. On the day of treatment 1. Fasting is required for 2 hours before and after oral administration of I-131, and moderate drinking is allowed. 2. Do not rub the thyroid gland after taking the drug. 3. On the day of treatment, patients with a history of “motion sickness” should avoid riding in a motor vehicle to prevent motion sickness and vomiting. After treatment 1. Pay attention to rest, avoid exertion and mental stimulation, drink more water and urinate more within 2 days after taking the medication. A few patients may experience weakness, nausea, itchy skin, swollen thyroid gland and other symptoms within a few days after treatment, as long as they pay attention to observation and symptomatic treatment. If individual patients have symptoms of thyroid pain, they can be given the necessary pain relief treatment. 3, pay attention to radiation protection after oral I-131 for a period of time, the patient will constitute a small amount of γ radiation to the surrounding near people, but the amount of radiation released in vitro is limited and will not cause a clear radiation hazard. Even so, according to the principle of radiation protection, it is recommended to keep more than 1.8 meters distance from others in fixed residence and avoid sharing utensils with others within 1 week after treatment. Within 2 weeks after treatment, close contact with infants and pregnant women should be avoided; those with childbirth plans should consider conception after six months. 4. In case of aggravation of symptoms, the thyroid hormones in stock in the thyroid tissue will still be released into the blood within 2 weeks after isotope treatment, which may cause aggravation of hyperthyroidism. In addition to continuing to take “beta-adrenergic receptor blockers” until the symptoms disappear, patients with severe hyperthyroidism can continue to take methimazole orally 3-7 days after isotope treatment and gradually reduce and stop the dosage in the following 4-6 weeks as the thyroid function becomes normal. 5. Insist on review Most patients will gradually have their symptoms relieved and disappear within 4 to 8 weeks after receiving isotope iodine treatment, and the size of the thyroid gland will shrink and return to normal. It is recommended to follow up within 1~3 months and at 6 months after treatment to evaluate the efficacy, and the interval of review can be gradually extended to once a year afterwards. 6. May need to be treated again After 3~6 months of treatment, if hyperthyroidism is still not in remission, isotope treatment can be performed again according to the condition. 7.If hypothyroidism occurs after treatment for hypothyroidism, levothyroxine sodium can be used for treatment, and the dose should be reviewed and adjusted regularly.