Skip to Main Content

Radioactive Iodine Therapy


Call or click for an in-person
or virtual visit.


Insurance Plans

View a list of insurance plans accepted at the University of Miami Health System.

Radioactive iodine (radioiodine, or RAI) therapy is a unique treatment only used to treat thyroid cancer and other thyroid-related conditions. Very few cells in your body can absorb iodine, so this treatment is well-suited to treat these conditions effectively.

Sylvester Comprehensive Cancer Center is designated by the National Cancer Center for its leadership and excellence in delivering state-of-the-art cancer treatments. We are the only NCI-designated cancer center in the Miami area.

We offer a multidisciplinary approach to ensure you have the best outcomes possible. Our radiation oncologists work closely with endocrinologists, surgical oncologists, radiologists, radiation safety experts, and nuclear medicine specialists to deliver the highest quality care and services available.

To help you prepare for RAI treatment, here are several things you need to know: 

What is radioactive iodine (RAI) therapy?

Radioactive iodine (RAI) therapy is used to treat certain types of thyroid cancer, as well as overactive thyroid (hyperthyroidism). It’s a radiopharmaceutical — a type of radioactive drug that can help with disease diagnosis and treatment. Even though it involves radiation and may sound scary, RAI is safe and reliable. It specifically targets your thyroid cells with little-to-no impact on your other cells, so it’s generally well-tolerated with few side effects.

How does RAI work?

Your thyroid gland, a butterfly-shaped gland that sits in the lower front part of your neck, is responsible for a variety of bodily activities, such as your metabolism and body temperature. To work properly, it relies on iodine, which is typically absorbed from the foods you eat. The thyroid absorbs RAI through the same method.

RAI is administered as a pill or liquid you can take at home, in the doctor’s office, or in the hospital. Your thyroid readily absorbs the radioactive iodine, making it easy to spot and diagnose any cancerous cells on scans. Higher levels of RAI, which can destroy cancerous cells, may be used for treatment. Within a few days, your body will naturally flush out any iodine that wasn’t absorbed.

How do you prepare for RAI therapy?

If you’re prescribed RAI, you’ll go on a low-iodine diet for approximately six weeks before treatment. This ensures that any iodine that shows up in your scans after treatment is from RAI and not any food you eat.

Your doctor will also administer two recombinant thyroid-stimulating hormone (TSH) injections into your muscle to help prepare your body for treatment. It also helps your thyroid tissue absorb the iodine.

How does RAI treat thyroid cancer, specifically?

RAI is most often used to treat the two most common types of thyroid cancer — papillary and follicular cancers. In most cases, the thyroid gland is removed prior to treatment, and RAI is used to kill any tiny pieces of thyroid cancer that might remain in your body.

An RAI dose can also help doctors pinpoint whether you still have any diseased thyroid tissue or if cancer has spread anywhere else in your body. Based on what they see in scans, they can decide whether you’ll need a higher RAI dose for further treatment.

How does RAI treat hyperthyroidism?

Because your thyroid produces many of your body’s hormones, hyperthyroidism basically puts your body into hyperdrive. You have a faster metabolism, but you also have a faster heart rate, more nervousness, difficulty sleeping, and you may feel shaky. For women, it can cause lighter or irregular periods.

Your thyroid relies on iodine for hormone production. As a result, RAI can treat hyperthyroidism by targeting and destroying your malfunctioning thyroid cells. In most cases, patients only need one RAI dose, but it can take several weeks or months for your symptoms to improve. You may need a second dose if your symptoms linger after six months.

Can RAI treat all thyroid cancers?

No, RAI is reserved for differentiated thyroid carcinomas that can absorb iodine, specifically papillary and follicular thyroid cancers. With these cancers, malignant cells closely resemble normal ones, and they grow slowly. Not every type of differentiated cancer can absorb iodine, however. RAI also offers no benefit to patients with medullary thyroid carcinomas.

What can you expect on treatment day?

On the day of your treatment, you can follow your normal morning routine, using the same deodorant, makeup, creams, etc. Take your medications like normal but ask your doctor if you should take your thyroid medication that day. Eat a light, low-iodine breakfast, such as oatmeal, at least two hours before treatment, but don’t eat within two hours of your appointment.

Before your treatment, you’ll have a nuclear scan. Then, you’ll be taken to a private room. Friends and family can stay with you until it’s time for your treatment, then they must leave. You’ll receive your RAI dose and your treatment.

Afterward, you will stay in your room alone for a few hours while we monitor your radiation levels. You may or may not feel side effects, such as nausea, dry mouth, neck or salivary gland swelling, at this time. Once you’re allowed to leave, you must drive yourself home — do not take public transportation or ride with family or friends. Drink plenty of fluids to flush any remaining radioactive iodine from your body.

Can you have RAI on your thyroid more than once, or is it too risky?

Yes, you can have RAI more than once if your thyroid cancer comes back or spreads somewhere else in your body. Because RAI is a treatment that specifically targets cancerous thyroid cells, it’s safe to use it no matter where your cancer may show up. Your chances of developing secondary cancer due to treatment are very low, but we carefully consider all the risks and details of your personal health before prescribing an RAI dose.

What side effects can you expect with RAI?

Depending on why you’re undergoing RAI, it’s possible to experience both permanent and short-term side effects. If you’re being treated for hyperthyroidism, RAI will likely trigger hypothyroidism — a condition where your thyroid doesn’t produce enough hormones. It’s a permanent condition, but it’s easily treated with lifelong hormone replacement therapy. With treatment for thyroid cancer, you may experience these temporary side effects:

  • Dry eyes
  • Dry mouth
  • Loss of taste and smell
  • Nausea
  • Neck tenderness or swelling
  • Swollen saliva glands
  • Watery eyes

What precautions should you take if you’ve had RAI?

For several days after your therapy, you’ll need to be careful around others to avoid exposing them to radiation. Your doctor can give you more specific instructions about how long you’ll need to take various precautions. In general, follow these safety measures:

  • Avoid close, lengthy contact with other people, especially pregnant women and children
  • Avoid public places
  • Don’t share a bathroom
  • Don’t share kitchen items, linens, towels, or any other personal items
  • Don’t travel via plane or public transit for three days
  • Shower daily
  • Stay at least 6 feet away from others for three days
  • Sleep alone in a separate bed (at least 6 feet away if in the same room)
  • Wash your dishes and clothes separately
  • Wash your hands frequently

RAI treatment may reduce sperm count in men, causing temporary infertility for up to two years. Men looking to start a family who may need several RAI doses may want to consider sperm banking.

Is there anyone who should avoid RAI therapy?

Yes, pregnant women and nursing mothers should not undergo RAI therapy. Wait at least six to 12 months after treatment before getting pregnant. If you’re breastfeeding, stop at least six weeks before you have RAI, and then, don’t restart.

Why Choose Sylvester?

Sylvester is an NCI-designated cancer center. The National Cancer Institute has recognized Sylvester for its outstanding work conducting research in its laboratories, treating patients in its clinics and hospitals, and reaching out to medically underserved communities with innovative prevention strategies.

Only center in South Florida with a specialty endocrine testing center. Our specialized testing centers improves diagnosis accuracy, leading to more precise treatments and better results. Located at the University of Miami Miller School of Medicine, the center is staffed by specialized nurses and technical assistants who perform complex hormone tests.

Leading-edge radiation therapy technology. From our pioneering work in MRI-guided techniques and HyperArc™ radiosurgery to our new addition of proton beam therapy, we can precisely target cancer cells with utmost accuracy. We offer advanced treatment options, including intensity-modulated radiation therapy, stereotactic body radiation therapy, stereotactic radiosurgery, and more, to improve outcomes, while preserving healthy organs and tissues.

More cancer clinical trials than any other South Florida hospital. If appropriate for your cancer and stage, our clinical trials provide you with easy access to the newest ways to treat and potentially cure your cancer.

Questions? We're here to help.

Our appointment specialists are ready to help you find what you need. Contact us today.