| "Taken 6-12 hours before exposure to radioactive iodine, KI fills the thyroid cells and prevents the gland from absorbing radioactive iodine. KI is also protective if taken within the first few hours after exposure to radioactive iodine. People should take one dose a day, only while they are being exposed to radioactive iodine and one day afterward. KI should be used only under instruction from local health authorities."
American Thyroid Association (ATA)