Thyroid Basics

Radioactive Iodine Treatment (RAI): All You Need to Know

By: Mary Shomon, Thyroid Expert

Average Read Time: 5 mins

You take a pill or drink that’s radioactive, and it essentially eliminates your thyroid function. Strange idea? Actually, it’s a common thyroid treatment, known as radioactive iodine (or RAI). 

RAI is also known as radioactive iodine ablation or radioiodine ablation, and it’s a frequently used treatment for Graves’ disease, hyperthyroidism (an overactive thyroid), and goiter (an enlarged thyroid). RAI is also used to treat some thyroid cancer patients after thyroid surgery. 

Because the thyroid is the only gland that absorbs iodine, doctors can specifically target the thyroid using RAI. The RAI is absorbed by the thyroid gland, where it destroys (ablates) an overactive or cancerous thyroid, without affecting other glands and organs. 

In most cases, the goal of RAI is to destroy thyroid tissue, which can eliminate thyroid cancer or reverse hyperthyroidism. Because it’s destroying the gland, RAI usually results in lifelong hypothyroidism.

RAI for Graves’ Disease/Hyperthyroidism

When RAI is used to treat Graves’ disease/hyperthyroidism, after treatment, the thyroid becomes less able to produce thyroid hormone. This process can, however, take up to six months. If your dose of RAI was insufficient, your doctor may recommend a second treatment to fully resolve your overactive thyroid.

While doctors attempt to give a dose of RAI that returns patients to the reference range, that outcome is not common. The majority of people who have RAI treatment eventually become hypothyroid and require thyroid hormone replacement medication for life.

RAI for Thyroid Cancer

RAI is commonly used as a follow-up treatment after surgery when you have a larger or more aggressive thyroid cancer, or when malignant thyroid nodules have features that suggest the cancer could become aggressive. The goal of RAI after surgery is to kill any remaining cancer cells to prevent recurrence of the cancer. 

Because cancerous thyroid cells don’t absorb radioactive iodine well, thyroid cancer patients are often taken off thyroid hormone replacement medication — or given several injections of another medication, Thyrogen — before RAI treatment. 

This helps the cells better absorb the RAI. Withdrawal of thyroid medication prior to RAI leaves patients feeling hypothyroid. The benefit of Thyrogen is that it helps relieve hypothyroidism symptoms, while still making the cells more sensitive to the RAI. 

Thyroid cancer patients are also typically asked to follow a low-iodine diet for two or more weeks before RAI treatment. The low-iodine diet also helps make the cells more able to absorb the RAI. 

After thyroidectomy and RAI treatment, you will become hypothyroid almost immediately, requiring thyroid-hormone replacement medication or life.

Your RAI Treatment

In the U.S, you usually won’t be hospitalized when you receive RAI, but you will receive your RAI treatment at a hospital or at your doctor’s office and not at home. RAI is administered orally, in pill form or as a liquid. If you’re getting RAI in pill form, you’ll likely get one to three pills to swallow with water. Liquid RAI is given in a small dose of a flavorless liquid. 

You’ll need to be isolated for several hours after your RAI treatment, and will be released to go home once your radiation levels are considered safe enough to leave. 

Getting Home After RAI

After treatment, you will be radioactive, and your doctor will recommend that you follow specific precautions to protect other people from radiation exposure

To start, you should not return home by any public transportation (like buses, the subway, trains, or an airplane). You can drive yourself, or have someone pick you up and take you home. Be sure, however, to sit as far away from anyone in a car as possible. 

Note: Even after you’re past the initial risk period, for several months after RAI you may emit low levels of radiation — enough to set off sensitive airport radiation detectors. If you fly, bring a doctor’s letter documenting your RAI treatment, or you may not be allowed to clear security.


Other Precautions After RAI

The length of time you need to follow precautions varies from around three days up to a week and depends on the RAI dosage you receive. 

Here are some guidelines:

Clearing the RAI From Your Body

Some radioactive iodine left over after RAI will be excreted by your body through urine, saliva, sweat, and bowel movements, and those bodily fluids will be radioactive for a period of time. 

To help speed up the process of clearing the RAI out of your system:

RAI Side Effects

While RAI does not typically have many side effects, you may experience: 

You may also develop swollen salivary glands, which can last several weeks. Experts recommend sucking on sour candies or chewing gum to stimulate saliva flow.

Radioiodine treatment can also cause dry eyes. Ask your doctor about lubricating eye drops if you experience this side effect. Also, be aware that if you wear contact lenses, you may want to switch to glasses for a period of time after the RAI for your comfort. 

Other RAI Considerations

RAI and Pregnancy: Doctors never knowingly perform RAI ablation on pregnant women, as iodine can cross the placenta and concentrate in the fetal thyroid gland, causing hypothyroidism. If you are of childbearing age, your doctor may perform a pregnancy test before RAI ablation. 

It is not recommended that you become pregnant until six months to a year after treatment. (Note: Thyroid surgery is a preferable treatment option for women with Graves’ disease or hyperthyroidism who want to become pregnant soon after treatment.) 

Also note that RAI may affect menstruation, with some women experiencing irregular periods for as long as a year after treatment. And, with irregular menstrual cycles, you may want to pay extra attention to ensuring that you have effective birth control, to avoid pregnancy in the year after RAI. 

RAI and Breastfeeding: Doctors don’t perform RAI ablation on women who are breastfeeding because the iodine can reach the baby via breast milk. This can negatively affect your baby’s thyroid gland and function. If you’re nursing and your doctor recommends RAI, you will need to stop breastfeeding. You can, however, safely breastfeed future babies. (Note: Again, thyroid surgery may be a preferable treatment option for nursing mothers with Graves’ disease or hyperthyroidism who want to continue breastfeeding after treatment.) 

RAI and Male Infertility: Men who receive higher doses of RAI or multiple RAI treatments for thyroid cancer can in some cases experience decreased sperm counts, resulting in temporary infertility, lasting for as long as two years. If you are planning to have children, talk to your doctor about whether sperm banking may be recommended.

Cancer Risk After RAI: If you get RAI treatment for thyroid cancer, your risk of developing certain secondary cancers increases. The degree of risk, however, is not clear, and some doctors believe that these secondary cancers are rare. The types of cancers associated with RAI treatment include:  

After RAI ablation, you should talk to your doctor about whether you should have periodic screening and monitoring for signs and symptoms of these secondary cancers.

Life After RAI

After surgery and RAI for thyroid cancer, you will become hypothyroid almost immediately. 

RAI for Graves’ disease/hyperthyroidism can take anywhere from a few weeks to a few months to fully ablate your thyroid. Keep in mind that once the thyroid has been partially or fully ablated, you will in most cases be hypothyroid, and require treatment with thyroid hormone replacement medication (such as levothyroxine or natural desiccated thyroid). Be sure to have your thyroid levels regularly tested after RAI, so that thyroid medication can be started as early as possible, to prevent you from becoming hypothyroid. 

Once you’re hypothyroid and taking thyroid hormone replacement, that’s the best time to focus on how to support your ongoing thyroid health. That’s where Thyroid Refresh comes in, with a wealth of information on diet, nutrition, sleep, stress management, fitness, and mind-body health, to help you feel and live well! 


About the Author

Mary Shomon is a patient advocate and New York Times bestselling author of 13 books on health. Mary has been researching, writing and teaching about thyroid disease, hormonal health, weight loss, and autoimmune disease for two decades. In addition to her books, you can find her writing at and, and catch her PBS Healthy Hormones television specials. Follow Mary on Facebook.