Nursing care
Radioactive Iodine Therapy: the nurse's role, start to finish
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
Radioactive iodine (I-131) therapy destroys overactive or malignant thyroid tissue, since the thyroid concentrates iodine more than any other tissue. After the dose, the patient is a radiation source for several days and needs specific precautions: separate utensils and linens, flushing the toilet twice, and avoiding close contact with pregnant women and young children.
What the procedure achieves
Radioactive iodine is used to treat hyperthyroidism, most commonly Graves' disease, and to ablate remaining thyroid tissue or metastases after thyroidectomy for thyroid cancer. The thyroid gland absorbs iodine preferentially, so the radioactive isotope concentrates almost entirely in thyroid cells and delivers a targeted dose of radiation that destroys the tissue over subsequent weeks.
The dose is calculated based on gland size, uptake studies, and the indication — ablative doses for cancer are typically much higher than doses used to treat hyperthyroidism. Effects are not immediate; thyroid hormone levels may take weeks to months to fall, and the patient may need interim symptom management while waiting for the gland to respond.
Pre-procedure nursing responsibilities
Confirm a negative pregnancy test before administration in any patient of childbearing potential, since I-131 crosses the placenta and can cause fetal thyroid ablation. Pregnancy is an absolute contraindication, and breastfeeding must be stopped well before treatment and not resumed for that infant.
Review the patient's medication list for anything that interferes with iodine uptake — amiodarone, iodinated contrast dye, and some thyroid medications need to be held for a specified period beforehand, per the treating physician's protocol. Confirm the patient understands and can follow the post-treatment isolation instructions before the dose is given, since compliance is the main safeguard against exposing others.
Equipment and positioning
I-131 is usually given as an oral capsule or liquid, administered in a shielded area by staff trained in radiation safety, often in nuclear medicine rather than on the general ward. No special patient positioning is required for the dose itself, but the room and any waste generated need to be handled under radiation safety protocols specific to the facility.
Nursing staff caring for the patient immediately afterward should minimise unnecessary time at the bedside and maintain distance where clinically appropriate, following the facility's radiation safety officer guidance on time, distance and shielding. Dosimeter badges are worn by staff with regular contact during this period.
Complications and early signs
Watch for nausea and vomiting in the hours after the dose, which can also increase radiation exposure risk if vomit is not handled per radioactive waste protocol. Sialadenitis — painful swelling of the salivary glands — is common in the first few days as the glands also take up some iodine.
In patients treated for hyperthyroidism, monitor for a transient worsening of thyrotoxic symptoms as damaged thyroid cells release stored hormone into circulation before the gland's activity falls — rarely this can progress toward thyroid storm in a poorly controlled patient. Longer term, hypothyroidism is an expected outcome rather than a complication, and most patients will need lifelong levothyroxine.
Post-procedure care
The patient is a radiation source for several days after the dose, with the exact duration depending on the amount given and local regulations. Instruct the patient to use separate utensils, dishes and linens from the rest of the household during this period, and to launder these separately.
The toilet should be flushed twice after each use, with the lid down, since excreted iodine is a primary route of radiation exposure to others. Close contact — sitting near, hugging, sharing a bed — with pregnant women and young children must be avoided for the duration specified by the treating team, often around five to seven days, sometimes longer for higher ablative doses. Sucking on hard sweets or sour sweets can help stimulate saliva flow and reduce salivary gland irritation.
What to teach before discharge
Give the patient written instructions covering exactly how many days each precaution applies, since verbal instructions given while still affected by the procedure are easily forgotten. Confirm they have someone who can shop or run errands for them if isolation at home is required, since some patients are advised to avoid public transport and crowded places for a short period.
Teach the signs of hypothyroidism to watch for over the following weeks and months — fatigue, weight gain, cold intolerance, constipation — since most patients treated for hyperthyroidism will eventually need levothyroxine replacement. Confirm the schedule for follow-up thyroid function tests, and stress that missing these appointments delays catching either an incomplete response or the expected shift into hypothyroidism.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our endocrine practice questions are the closest set to what this page covers.
Common questions
How long is a patient radioactive after I-131 therapy?
It varies with the dose given, but patients typically need to follow precautions for several days, often five to seven, sometimes longer after high ablative doses for cancer. The treating nuclear medicine team gives an exact timeframe based on the specific dose.
Why does the toilet need to be flushed twice?
Radioactive iodine is excreted primarily in urine, so a single flush may not clear all residual radioactivity from the bowl. Flushing twice with the lid down reduces the radiation dose to anyone else using that bathroom.
Can a pregnant nurse or pregnant family member be near this patient?
No. Pregnant women should avoid close contact with the patient for the full precaution period, since the developing fetus is highly sensitive to radiation exposure even at a distance that would be safe for other adults.
Is hypothyroidism after radioactive iodine therapy a complication?
It's generally an expected outcome rather than a complication, particularly when treating hyperthyroidism, since the goal is to reduce overactive thyroid tissue. Most patients will need lifelong levothyroxine and regular thyroid function monitoring afterward.