At a glance
Radioactive iodine therapy is a nuclear medicine treatment that uses a radioactive form of iodine to destroy overactive or cancerous thyroid tissue without surgery.
The thyroid gland, a butterfly-shaped gland in the front of the neck, naturally absorbs almost all the iodine the body takes in. When you swallow a capsule or liquid containing radioactive iodine (called iodine-131), the thyroid cells draw it in just as they would ordinary iodine. The radiation then damages or destroys those cells from the inside, while surrounding tissues receive very little exposure because iodine-131 travels only a short distance in the body.
Medical Condition
Doctors recommend radioactive iodine therapy for conditions where the thyroid gland is producing too much hormone or where thyroid cancer cells need to be eliminated after surgery.
- Hyperthyroidism (overactive thyroid) caused by Graves' disease, an autoimmune condition that overstimulates the gland
- Toxic nodular goitre, where one or more lumps in the thyroid produce excess hormone independently
- Differentiated thyroid cancer (papillary or follicular type) as follow-up treatment after surgical removal of the thyroid, to destroy any remaining cancer cells
- Recurrent or metastatic differentiated thyroid cancer, where cancer has come back or spread to lymph nodes or other organs
Radioactive iodine is not suitable for every patient. Your specialist will weigh up several factors before recommending it.
- Pregnancy: the treatment can severely harm a developing baby and is never given during pregnancy
- Breastfeeding: iodine-131 passes into breast milk, so treatment is delayed until breastfeeding has stopped
- Anaplastic or medullary thyroid cancer: these types do not absorb iodine, so the treatment has no effect on them
- Severely reduced kidney function: the kidneys clear iodine-131 from the body, and poor kidney function can prolong radiation exposure
Risks & Complications
Radioactive iodine therapy is generally well tolerated, but like any medical treatment it carries recognised side effects and risks.
- Hypothyroidism (underactive thyroid): the most common outcome after treatment for hyperthyroidism or thyroid cancer; the thyroid produces too little hormone and lifelong thyroid hormone replacement tablets are usually needed
- Neck tenderness or swelling: mild inflammation of the remaining thyroid tissue in the days after treatment
- Dry mouth and reduced saliva: iodine-131 can affect the salivary glands (the glands that make saliva), causing temporary or, less often, lasting dryness
- Nausea: usually mild and short-lived, most noticeable in the first day or two
- Temporary worsening of eye symptoms in Graves' disease: patients who already have eye inflammation may notice a brief flare
- Altered taste: some patients notice a metallic or changed sense of taste for a few weeks
- Radiation precaution period: patients must limit close contact with others, especially children and pregnant women, for a period set by the treating team
- Very small long-term risk of secondary cancers from radiation exposure, which doctors weigh against the benefits when deciding on treatment
Preparation & Procedure
Preparation for radioactive iodine therapy begins weeks before the actual treatment day, because the thyroid must be primed to absorb as much iodine-131 as possible.
A low-iodine diet is usually followed for one to two weeks before treatment. This means avoiding iodised salt, seafood, dairy products, eggs, and foods that list iodine or iodate among their ingredients. The goal is to make the thyroid iodine-hungry so it takes up the radioactive dose eagerly. Your medical team will provide a specific food list.
Thyroid hormone levels need to be elevated before treatment for thyroid cancer, because high levels of thyroid-stimulating hormone (TSH, the signal from the brain that tells the thyroid to work) make cancer cells absorb iodine more effectively. This is achieved either by stopping thyroid hormone replacement medication for several weeks under medical supervision, or by injections of synthetic TSH given over two days before treatment. For hyperthyroidism, this step is usually not required.
Several medications interact with the treatment. Antithyroid drugs (medications that slow thyroid hormone production) are usually paused before the procedure. Iodine-containing contrast dyes used in CT scans, amiodarone (a heart medication), and certain supplements containing kelp or seaweed can all reduce the thyroid's uptake of iodine-131 and may need to be avoided for weeks to months beforehand. Your doctor will review your full medication list.
Preliminary tests often include blood tests to measure thyroid hormone levels and TSH, a thyroid uptake scan (a small test dose of radioactive iodine to see how well the gland absorbs it), and sometimes imaging such as ultrasound of the neck or a whole-body scan.
On the treatment day, the steps typically follow this sequence:
- You arrive at the nuclear medicine unit, usually fasting for a few hours as instructed
- The team confirms your identity and reviews your consent, diet compliance, and any recent medications
- A capsule or liquid containing iodine-131 is prepared; the dose is calculated in advance based on your condition, thyroid size, and uptake results
- You swallow the capsule or drink the solution; the procedure itself takes only a minute or two
- You drink extra fluids to help flush iodine-131 through the kidneys
- Depending on the dose and local regulations, you may be monitored in a shielded room for several hours or overnight, or you may be discharged the same day with detailed radiation safety instructions
Aftercare
Recovery after radioactive iodine therapy focuses on two things: radiation safety for people around you, and monitoring your thyroid function as it changes in the weeks ahead.
- Radiation precautions: your medical team will tell you exactly how many days to sleep in a separate room, avoid close contact with children or pregnant women, use separate towels and cutlery, and flush the toilet twice after use; follow these instructions precisely as they are based on the dose you received
- Stay well hydrated in the first few days to help your kidneys clear iodine-131 from the body quickly
- For cancer patients, a whole-body scan is usually performed five to ten days after treatment to confirm where the iodine-131 was taken up
- Blood tests to check thyroid hormone levels and TSH are repeated at intervals set by your endocrinologist (hormone specialist), typically at four to six weeks and again at three to six months
- If your thyroid becomes underactive after treatment, your doctor will start you on thyroid hormone replacement tablets, which you take once daily; the dose is adjusted over time based on blood results
- Thyroid cancer patients remain on slightly higher doses of thyroid hormone to keep TSH low, which reduces the chance of cancer cells being stimulated to grow
- Women are advised to avoid pregnancy for at least six months to one year after treatment; men are similarly advised to wait before trying to conceive, as iodine-131 can temporarily affect reproductive cells
- Drink plenty of fluids and suck on sour candy in the first week to keep saliva flowing and reduce the chance of lasting dryness in the salivary glands
- Follow-up imaging, such as neck ultrasound or a repeat whole-body scan, is scheduled at intervals determined by your treatment team based on your diagnosis
Cost & What Determines It
The cost of radioactive iodine therapy varies considerably depending on why it is being given, where it is performed, and how much follow-up care is built into the package.
- Diagnosis and disease stage: treating hyperthyroidism typically requires a lower dose than post-surgical cancer ablation (destruction of remaining cancer tissue), and recurrent or metastatic cancer may require repeat treatments, each adding to the total cost
- Dose calculation and preparation: the iodine-131 dose is custom-prepared based on a preliminary uptake scan and thyroid size measurements, and the cost of these pre-treatment tests varies between facilities
- Inpatient versus outpatient setting: higher doses, such as those used for cancer treatment, often require an overnight stay in a shielded room to meet radiation safety regulations, while lower doses for hyperthyroidism may be given on an outpatient basis
- Hospital class and country: private specialist nuclear medicine centres in higher-cost countries charge more than facilities in countries where medical travel is common
- Synthetic TSH injections: if required instead of stopping thyroid hormone medication, these injections add a significant line to the bill
- Post-treatment whole-body scan: usually performed a few days after the dose and may or may not be included in a quoted package price
- Endocrinology consultations and blood tests: pre-treatment and follow-up appointments, TSH and thyroid hormone blood panels, and any additional imaging
- Length of stay: patients travelling from abroad often need to remain in the destination city for the mandatory post-treatment scan before flying home, adding accommodation costs
A hospital package for this therapy typically covers the nuclear medicine consultation, the calculated dose of iodine-131, basic nursing care during any inpatient observation period, and sometimes the first post-treatment scan. Items commonly billed separately include the preliminary uptake scan, synthetic TSH injections, thyroid hormone medication, additional blood tests, specialist endocrinology follow-up visits, and any management of side effects such as dry mouth or neck discomfort.
BPJS Kesehatan and most Indonesian private health insurance plans do not cover treatment received abroad, which means most patients who travel for this therapy pay out of pocket or use an international health insurance policy that explicitly includes overseas medical care. Asking the hospital for a written cost estimate that lists each item individually before you travel is the most reliable way to understand your actual financial commitment and avoid unexpected charges on arrival.
Frequently Asked Questions
How many sessions of radioactive iodine therapy will I need?
Most patients need only one session, though some may require a second dose if the first does not fully achieve the treatment goal. Your nuclear medicine doctor will check how your body responded, usually with a follow-up scan or blood test, before deciding whether another dose is needed.
What does radioactive iodine therapy feel like?
The treatment itself is painless because it is given as a capsule or liquid you swallow, not as an injection or surgery. In the days that follow, some people notice mild neck soreness, a dry mouth, or a feeling of nausea, because the thyroid gland (the butterfly-shaped gland in your neck that this therapy targets) absorbs the iodine and becomes temporarily inflamed. Most of these sensations settle on their own within a week or two.
How soon will radioactive iodine therapy start working?
Changes begin inside the thyroid within days of swallowing the dose, but the full effect on hormone levels usually takes several weeks to a few months to become clear. Your doctor will schedule blood tests at regular intervals to track progress and decide whether any adjustment to your care is needed.
How much does radioactive iodine therapy cost?
The cost depends on factors specific to your situation, including the dose of radioactive iodine required, whether you need a preparatory period of hormone withdrawal or special injections beforehand, the class of hospital or nuclear medicine facility, and the length of any isolation stay required for radiation safety. A written estimate from the hospital, based on your medical records, is the most reliable way to understand what you would actually pay.
This page is general information, not a substitute for medical advice. Every case is different. Your doctor decides what is right for you.
