How Potassium Iodide (KI) Works
KI is a pill or liquid that can be used in radiation emergencies that involve radioactive iodine. KI contains non-radioactive iodine. Non-radioactive iodine helps prevent radioactive iodine from being absorbed by the thyroid gland.
The thyroid gland cannot tell the difference between non-radioactive and radioactive iodine. It will absorb both kinds.
KI works by keeping radioactive iodine out of the thyroid gland where it can cause damage. When a person takes KI, the thyroid absorbs the non-radioactive iodine in the medicine. Because KI contains so much non-radioactive iodine, the thyroid becomes “full” and cannot absorb any more iodine—either stable or radioactive—for the next 24 hours.
KI does not keep radioactive iodine from entering the body and cannot reverse the health effects caused by radioactive iodine once the thyroid gland is damaged.