Doing a second treatment with iodine 131 usually requires stopping the medication for more than two weeks. Iodine 131 treatment is indicated for patients with hyperthyroidism who need to stop taking their thyroid medication for more than two weeks before having the treatment. Since thyroid medications inhibit the uptake of iodine by the thyroid gland, thus affecting the effectiveness of the treatment, they need to be discontinued prior to treatment to ensure good results. After iodine 131 treatment, most patients do not have significant adverse reactions, a few patients may experience nausea, fatigue, decreased appetite and other symptoms, individual patients may be due to the role of ionizing radiation, resulting in a large release of thyroid hormones into the blood caused by thyroid crisis, which needs to be dealt with in a timely manner. It is recommended that patients consult the doctor before treatment for matters requiring attention, prepare according to the doctor’s instructions, relax and actively cooperate with the treatment.