I-131 therapy side effects: what to know

Because radioactive iodine is taken up by thyroid tissue and some saliva-producing glands, you may notice a sore throat, neck tenderness, dry mouth, altered taste or swollen salivary glands. Nausea can occur after the dose. Some people have few symptoms, while others need help controlling discomfort.

Effects can be temporary or last longer. The treatment team considers your symptoms alongside thyroid blood tests, examination and the reason for therapy. New symptoms are not automatically evidence that treatment has failed.

Drink fluids according to your team’s instructions, use the mouth-care measures they recommend, and choose soft foods if swallowing is uncomfortable. Take only medicines approved by the team, particularly if you have kidney disease or other conditions.

Keep every follow-up appointment. Tell the team about persistent dry mouth, dental problems, repeated vomiting, voice changes or neck swelling so they can assess and treat the cause.

Seek urgent medical help for difficulty breathing, rapidly increasing neck swelling, inability to swallow fluids, collapse or signs of a severe allergic reaction. Contact your treatment team promptly for fever, ongoing vomiting, severe pain or dehydration symptoms such as very little urine.

Ask which effects are expected for your dose, what mouth care is appropriate, when blood tests are due, how long radiation precautions continue, and which number to use for urgent advice.