Potassium iodide, also called KI, only protects a person’s thyroid gland from exposure to radioactive iodine. KI will not protect a person from other radioactive materials or protect other parts of the body from exposure to radiation. KI is most effective if taken before exposure or immediately after exposure. Since there is no way to know at the time of an incident whether radioactive iodine was present in the release, taking KI would probably not be beneficial. Also, KI can be dangerous to some people.