Iodine 131 treatment for hyperthyroidism radiation usually goes away in about a month. Iodine 131 is a drug used to treat hyperthyroidism by destroying the thyroid gland with radioactive radiation. The effective half-life of iodine 131 in the thyroid gland is about 35 to 45 days, and a single therapeutic dose can have a sustained effect on the thyroid for up to 30 to 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 utensils with others. With the development of time after iodine 131 treatment, hypothyroidism may occur in some patients, and it is necessary to review the thyroid function triple test on a regular basis. If hypothyroidism occurs, levothyroxine tablets should be taken instead of the treatment under the instruction of the doctor.