Side effects of radioactive iodine pills when used to treat hyperthyroidism include dry mouth with metallic taste, sore throat, swollen or painful neck, mild nausea or vomiting, constipation, diarrhea and fatigue. Unusually low or high thyroid levels have also been observed, as stated by WebMD.
Radioactive iodine pills are used to treat hyperthyroidism and certain kinds of thyroid cancer, notes Drugs.com. Once swallowed, the radioactive iodine pills are absorbed by the thyroid gland causing it to shrink and the symptoms of hyperthyroidism to subside within three to six months, explains Mayo Clinic. The radiation caused by the pills does not increase a person's risk of getting thyroid cancer, in fact, radioactive iodine treatment has been used to safely treat millions of people for decades, as observed by WebMD.
People under radioactive pill treatment are advised to follow some guidelines to avoid exposing others to radiation. These include keeping a distance from people, especially women and children; avoiding close contact, kissing or sexual intercourse; sleeping alone in a separate room; separately using and washing towels, sheets and clothes for a week; flushing the toilet twice after each use; and rinsing the sink and tub thoroughly after use, as recommended by WebMD.