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After radioactive iodine treatment

Find out what happens after having radioactive iodine treatment.

After having treatment

For a few days after radioactive iodine treatment, you will be slightly radioactive. Every day the doctors will come and take measurements from you to work out how much radiation is left in your body. They will tell you when the radioactivity has dropped to a safe level and you can go home.

If you had to stop taking your thyroid hormone tablets, your nurse will tell you when you can start to take them again. Usually, this is 3 days after your treatment.

You will need to take thyroxine tablets to replace the hormones that your thyroid gland normally makes. Your doctors will want to keep your thyroid hormones at a slightly higher level than you would normally need. This is to stop your body producing another hormone called thyroid stimulating hormone (TSH). TSH can help some types of thyroid cancer cells to grow.

Radiation safety precautions

There are safety precautions you may need to follow afterwards. This is because the treatment is radioactive. 

The advice about precautions varies for different people and for different hospitals. So make sure you talk to your doctor or specialist nurse. They will explain how long you need to limit yourself.

These precuations include:

Your doctor might tell you not to have close contact with babies, young children, pets or pregnant women for a couple of weeks. You might also need to stay away from crowded places where you may be close to the same person for a long time, such as the cinema.

You might need to sleep in a separate bed if you normally share a bed. Check if this applies to you and ask how long this should be for.

You might need to avoid sexual intercourse for a period of time or to use a condom. Check if this applies to you and ask how long this should be for.

It is also recommended that:

  • women use reliable contraception for at least 6 months
  • men use reliable contraception for at least 4 months

This is because the eggs and sperm produced after treatment may be damaged by the radiation. This could cause abnormalities in a child conceived soon after the treatment. Research suggests that if you wait for the advised period of time, you don’t have an increased risk of abnormalities with future pregnancies or children.

Travelling after radioactive iodine treatment

If you are planning to travel abroad you should be aware that recent treatment with radioactive iodine may set off radiation alarms at airports. This could happen up to 12 weeks after your treatment.

To avoid problems make sure you take a certificate from the hospital, or a letter from your doctor, telling about the treatment you have had.

Possible short term side effects

The side effects of radioactive iodine treatment vary depending on your age, whether you have other medical conditions and the dose of radioactive iodine you have. Some people may have one or more of the following short term side effects:

This is where you spit is made. You can have painkillers to help with the inflammation.

If you have a dry mouth, your nurse can give you artificial saliva. You may also have short term changes to your taste and smell. This may not start until you get home. It usually gets better within 4 to 8 weeks. It can help to drink plenty of fluids after your treatment.

This is where your spit is made. Your salivary glands can become inflamed after treatment. This can cause symptoms such as swelling and pain, and making less spit. This usually gets better with time, but in a few people it may be permanent.

To reduce the risk of getting this side effect, it can help to drink plenty of fluids during your hospital stay. And some doctors recommend that you chew gum or suck sweets to keep the salivary glands working.

Some people may have a feeling of tightness or swelling in their neck for a few days after treatment. This is more common if you still had a large part of your thyroid gland when you have radioactive iodine treatment. Some people also feel flushed. Rarely, people can feel pain in their neck.

Tell your doctor or nurse if any of these symptoms happen. They can give you a painkiller or a medicine to reduce inflammation, which can help.

You may feel sick for the first few days after treatment. Your doctor or nurse can give you anti sickness medicine to help with this.

Possible long term side effects

Possible long term side effects include:

In women, radioactive iodine treatment should not affect the ability to have children, even if you need to have repeated treatments. Some women may have irregular periods after treatment.

Men who need to have repeated treatment with radioactive iodine may have lower sperm counts and lower testosterone levels. This usually gets better with time. Rarely, it means that you may be unable to father a child (be infertile). Your doctor may offer you sperm banking before you start treatment.

After this treatment, doctors usually recommend that women wait for at least 6 months and men for at least 4 months before trying to conceive a baby. The research suggests that if you wait for the advised period of time, you don't have an increased risk of abnormalities with future pregnancies or children.

For a few people, inflammation of the salivary gland can be a long term problem. This may cause a dry mouth and permanent changes in taste and smell.

It is common for people to feel very tired for up to a year after treatment. But energy levels will usually return to normal levels. Most people get back to leading a normal life.

Radioactive iodine treatment can affect the lacrimal glands. These are glands in your eyes which make tears. The treatment can affect the production of tears. Some people may develop dry eyes and rarely, some people get watery eyes.

Bone marrow is the spongy substance in the centre of the bones that makes red and white blood cells and platelets. The treatment may stop the bone marrow making so many blood cells. If this happens you may have lower resistance to infection, and tiredness and breathlessness. Or you may notice that you bruise or bleed more easily.

You may need to have blood tests to monitor your blood cell levels. It is rare for this to be a long term problem after radioactive iodine treatment.

Some people need to have repeated radioactive iodine treatment for thyroid cancer that has spread to the lungs. Very rarely, they may develop problems with their lungs.

The treatment makes the lung tissue less stretchy. This is called radiation fibrosis, and can make it harder to breathe. Your doctors will keep an eye on your lung function.

After this treatment, you may have a slightly increased risk of developing a second cancer in the future. Doctors are not sure exactly how much your risk is increased. But most studies suggest it is a very low increase in risk.

Your doctor or nurse specialist will discuss this with you if you are worried. They can help you weigh up this risk with the benefit of treating the thyroid cancer.

Further radioactive iodine treatments

It is quite common for people to need more than one radioactive iodine treatment. This is to make sure the treatment destroys all the remaining thyroid tissue and cancer cells.

Last reviewed: 
13 Nov 2014
  • Head and Neck Cancer: A Multidisciplinary Approach
    LB Harrison, RB Sessions and WK Hong
    Lippincott Williams & Wilkins, 2009

  • Cancer and its management (6th edition)
    J Tobias and D Hochhauser
    Wiley-Blackwell, 2010

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