Iodine-131 is radioactive iodine, and the side effects are as follows: 1. Some patients may experience neck swelling and pain or swelling for a short period of time after taking iodine-131, but the discomfort can be gradually relieved within a week; 2. The patient may experience symptoms such as dry throat, sore throat and even general weakness, and the symptoms will be relieved after a week of rest; 3. The patient’s glandular tissues may also absorb iodine-131 during the treatment, and the glandular cells will be destroyed after absorption, resulting in abnormal taste.