131 iodine is clinically referred to as iodine-131, which is mainly used for the treatment of hyperthyroidism. After treatment, the previously enlarged thyroid gland will shrink and play the role of antagonizing hyperthyroidism. Precautions can be taken in the following aspects: 1. Dietary attention: Iodine-131 treatment should be followed by at least 2 hours before eating. On the day of treatment, patients are advised to drink more water to promote the excretion of iodine in the body and not to eat foods with high iodine content, such as seaweed, nori and seafood foods, for 1 month to avoid affecting the therapeutic effect. 2. Keeping distance: Iodine-131 treatment uses beta-rays for the destruction of thyroid tissue. Therefore, it is recommended to avoid close physical contact with others, especially pregnant women, children and the elderly, and to keep a proper distance from them. The level of thyroid hormone will not return to normal immediately after treatment, and the level of thyroid hormone can only be restored when the thyroid tissue is completely fibrotic, so patients will experience a high level of thyrotoxicosis after treatment. It is recommended that after treatment, patients should be monitored and rested to avoid infection. In addition, there will be swelling in the front of the neck, which usually does not require treatment and can be relieved by itself; if the pain worsens, consult your doctor promptly. 4. Some patients may experience an increase in protrusion after treatment; 5. Prepare for pregnancy: Female patients should consider pregnancy at least six months after treatment, while male patients should consider pregnancy at least four months later, depending on the patient’s recovery status; 6. Usually, iodine-131 does not affect blood and liver functions, but some patients may have abnormal blood and liver functions during the course of taking medication after treatment. Iodine-131 therapy is one of the three types of hyperthyroidism treatment and is relatively safe. It is a good choice when there is discomfort or allergy to oral antithyroid drugs, but after receiving treatment, it is still necessary to conduct regular review and follow-up, and pay attention to personal protection under the guidance of a specialist to achieve better results.