Radioactive Iodine Therapy for Thyroid Cancer: Inpatient Treatment

This information explains radioactive iodine therapy to treat thyroid cancer in the inpatient setting.

Treatment with radioactive iodine helps reduce the risk that thyroid cancer will come back. It is also used to treat thyroid cancer that has spread.

Radioactive iodine enters your bloodstream and is taken up by your thyroid cells. The radioactivity destroys the cancer cells.

Before Your Treatment

Discuss your treatment plan

Your doctor will discuss your treatment plan with you. It will consist of the following steps:

  • You will have blood tests and receive a thyrotropin alfa (Thyrogen®) injection to help prepare for your treatment.
  • The next day you will receive another injection and a small diagnostic dose of radioactive iodine and you will have whole body scans. You will not have to follow any precautions after you receive the dose.
  • The following day you will be admitted to the hospital for your treatment. Most people are in the hospital for 1 night. Your doctor will tell you if you will need to stay longer.
    • The radioactive iodine is usually given in pill form, but it can also be given in liquid form. Some people have trouble swallowing pills. If you do, tell your doctor in Nuclear Medicine before your treatment.
  • You will have another whole body scan after your treatment. This will allow your doctor see where the radioactive iodine was taken up in your body.

You will need to avoid getting pregnant or avoid getting your partner pregnant for at least 6 months after getting radioactive iodine therapy or as directed by your doctor. Make sure you use birth control after treatment for 6 months to 1 year after you receive this treatment. If you plan to get pregnant or father a child, speak with your doctor about this before your treatment.

Stop breastfeeding

If you are breastfeeding or pumping breast milk, you will need to stop at least 6 to 12 weeks before you receive this treatment. This is because the radioactive iodine collects in your breast tissue. Talk with your doctor or call the Department of Medical Physics at 212-639-7391 if you have any questions about breastfeeding and your treatment.

Contact your insurance company

Once your doctor has given you your treatment plan, call your insurance company to find out if you need preauthorization for any treatments and tests. Your doctor’s office and the hospital will not know this information. If you need help with preauthorization, contact Patient Billing at 646-227-3378.

Follow a low-iodine diet

If you have iodine in your diet, it can prevent your thyroid from taking up the radioactive iodine. You will need to follow a low-iodine diet for 1 to 2 weeks before you start treatment. A low-iodine diet will make your radioactive iodine therapy more effective. Follow this diet until your test or treatment is complete. Your nurse will give you the resource Low-iodine Diet.

Note the time of your treatment

A clerk from the Admitting Office will call you after 2:00 pm the day before your treatment. They will tell you when to arrive for your treatment. If you do not receive a call by 7:00 pm, please call 212-639-7881.

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The Day of Your Treatment

On the morning of your treatment, follow these guidelines.


  • You can shower with soap and water the night before or the morning of your treatment.
  • You can apply your usual deodorant, lotions, creams, and makeup.


  • Take your thyroid medication if your doctor tells you to take it.
  • Take all of your other usual medications.


  • Continue to follow a low-iodine diet.
  • Eat a light breakfast, such as oatmeal.
  • Your treatment will probably be in the afternoon, so bring a light lunch or snack. Your first delivered meal will be dinner, which will be served in your room after your treatment is finished.

What to bring

You will be staying in a private room. It will have a telephone, TV and DVD player, and a bathroom. You can bring the following items with you:

  • Comfortable clothes to wear during the day.
  • Sleep wear.
  • Toiletries, such as soap, a toothbrush, deodorant, shampoo, and conditioner.
  • Sanitary pads, if you expect to be menstruating at that time.
  • Sour hard candy to help with the dry mouth that some people experience after treatment. Your doctor will tell you when to start sucking on them.
  • Books, magazines, laptop computer, DVDs, a cell phone, and other items to help pass the time.

You can take these items home with you after your treatment. Any small amounts of radiation on these items will not harm you or anyone else

Where to go

Enter the hospital through the Schwartz Building at 1250 First Avenue (between East 67th and East 68th Streets). Turn left by the security guard’s desk, go up a short flight of stairs, and check in at the Nuclear Medicine reception desk. Please arrive on time.

What to expect

You will be taken to a private hospital room as soon as it is available. You will be treated the day you arrive. Your friends and family can stay in your room before treatment, but must leave before you get your treatment.

Your doctor and radiation safety officer will come to your room to answer your questions and discuss the precautions you must follow after your treatment. You will be given a written copy of these instructions. You will then be asked to sign a consent form.

Before your treatment begins, your nurse will evaluate you. You will be given medication to prevent nausea or vomiting. Do not eat for 2 hours after you have taken this medication

During your treatment

You will get your dose of radioactive iodine. It will be based on the results of your blood tests and scans. You will get water to swallow the dose.

  • The pill form of radioactive iodine comes in capsules about the size of a vitamin. The dose is usually given with 1 to 4 pills.
  • The liquid form of radioactive iodine is about 5 milliliters, or about a teaspoon. You will drink it out of a small vial through a straw. The liquid is clear and has little to no flavor. Most people say it tastes like water, though some say that it has a slightly stale or musty taste.

After you receive your treatment, you must stay in your room at all times. The door to your room can stay open. Your visitors must stay outside your room, but they can talk to you from the doorway.

You will need to start sucking on sour hard candies after your treatment. Your doctor will tell you when to start doing this.

The hospital staff that will be taking care of you has been trained in radiation safety. They may enter your room but they will have to limit the time they spend with you. They will speak with you from the doorway if they do not need to enter your room. Please tell your nurse if you need help or have any problems such as nausea or an upset stomach.

To limit the amount of radiation that gets on things in your room, protective covers will be placed on your phone, bedside table, and wash basin. A disposable mat will be put by the toilet. You will have a container to throw away your trash. A radiation safety staff member will remove all trash daily.

You may not experience any side effects of the radioactive iodine right after you receive it, but you may have side effects later. These are described in the “Side Effects” section below.

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After Your Treatment

The morning after your treatment, the radiation level in your body will be measured. Once the level is low enough, you will be discharged. Most people can leave the morning after treatment. Sometimes, radiation stays in the body longer than expected. In that case, you will need to stay in the hospital until the level is safe.

Clearing the radioactive iodine from your body

Some of the radioactive iodine will be taken up by your thyroid cells, but the remainder will exit your body quickly. Most of the remaining iodine will exit your body in your urine, but smaller amounts will also exit your body in your saliva, sweat, and stool.

To help the iodine exit your body quickly:

  • Drink plenty of liquids. Try to drink at least 1 cup of liquid every hour while you’re awake. Do this for 2 to 3 days after your treatment. You do not have to wake up at night to drink liquids.
  • Urinate often. Since your urine will be radioactive, you must take extra care to contain it. Women can urinate as usual. Men must sit when urinating.
  • Move your bowels regularly to reduce the dose of radiation to your intestines. If you are often constipated, ask your doctor about taking laxatives before your treatment. If you do not have a bowel movement within 24 hours after your treatment, call your doctor.
  • Call your nurse if you have any problems, such as nausea or an upset stomach.


  • You can resume your usual diet the day after your treatment, unless instructed by your doctor.
  • Continue to drink plenty of liquids for 2 to 3 days after your treatment.
  • If you drink alcohol, do so in moderation.


  • If you were told to stop taking your thyroid medications, start taking them again the day after your treatment.
  • Take all other prescribed medications as instructed by your doctor.


  • Do not travel by plane, train, subway, or bus for the first 24 hours after you are discharged. This is to make sure you are not in close contact with other people for long periods of time. Even a short subway ride could become long if the train gets stuck or delayed.
  • You will receive a card to show to authorities, if needed. The card states that you received treatment in Nuclear Medicine and that you may give off small amounts of radioactivity for up to 1 month after your treatment. Use it if you are stopped by law enforcement at a checkpoint, such as the airport or outside a tunnel.

Using your cell phone

You can use your cell phone without any restrictions.

Returning to work

Your radiation safety officer will tell you when you can go back to work.

Sexual activity

  • Your doctor or radiation safety officer will tell you when it’s safe to resume sexual activity.
  • Ask your doctor or nurse about using birth control. You will need to avoid becoming pregnant or getting someone pregnant for at least 6 months.
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Side Effects

You may experience the following side effects after your treatment:

  • Mild nausea right after you take the radioactive iodine. You will receive antinausea medication before your treatment to prevent this.
  • Swelling in your cheeks from irritation or damage to your salivary glands. This can occur as early as the morning after your treatment and continue as long as a year after your treatment. Call your doctor if you have:
    • Painful, swollen glands
    • Foul-tasting saliva
    • Bad-smelling saliva
  • Dry mouth, which is caused by irritation or damage to your salivary glands. This is rare with smaller doses of radioactive iodine. Dry mouth can occur right after treatment or it can occur for several months to a year after treatment. Drink plenty of liquids, as instructed. Sucking on sour hard candy after your treatment can help.
  • Changes in taste caused by irritation of your taste buds. You may notice that food tastes salty or metallic after your treatment. This is temporary and usually goes away within 8 weeks after your treatment. Try foods with different flavors to ensure you are getting the nutrition you need.
  • Neck pain. This can occur during the first 2 to 3 weeks after your treatment, but it depends on the amount of thyroid tissue still in your neck. A mild pain reliever such as acetaminophen (Tylenol®) should help.

In very rare cases, the treatment can cause enough swelling to make it hard to breathe. This is a serious condition. If you have trouble breathing, go to your nearest hospital emergency room immediately. Have them call your doctor at Memorial Sloan Kettering (MSK).

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Follow-up Care After Your Treatment

About 1 week after your treatment, you will return to Nuclear Medicine. You will have a scan to see where the radioactive iodine was taken up in your body. You will get an appointment card before you go home. Call 212-639-6652 if you have any questions about the scan.

Your doctor may also:

  • Order other scans based on your healthcare needs.
  • Order blood tests to see if the dose of your thyroid medication needs to be changed.

After your first follow-up appointment, you will need to make a follow-up appointment for 6 months later.

Support for survivors

At MSK, care doesn’t end after active treatment. The Resources for Life After Cancer (RLAC) Program is for patients and their families who have finished treatment. This program has many services, including support groups, seminars, workshops, support groups, counseling on life after treatment, and help with insurance and employment issues. For more information, call 646-888-8106.

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American Cancer Society


American Thyroid Association

National Cancer Institute (NCI)


Light of Life Foundation


ThyCa: Thyroid Cancer Survivors’ Association, Inc.


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