It is used to supply iodine in the form of vitamin tablets or pills. It can be added to table salt to prevent a deficiency of iodine. It is also used to make silver iodide. It can be used to add iodine to organic compounds. It is used to prevent thyroid cancer by filling up the thyroid with normal iodine. After a nuclear explosion there normally is radioactive iodine in the air. The radioactive iodine collects in the thyroid and causes cancer. When the person takes potassium iodide it fills up the thyroid with iodine so no radioactive iodine can come in. 