After radioactive iodine treatment for thyroid cancer

Having radioactive iodine treatment means you will be radioactive for several days afterwards. You will be able to go home from hospital when the radiation level in your body is at a safe level. As you will still have some radioactivity in your body you may still have to take some precautions when you go home. Your healthcare team will explain everything to you.

Thyroid medicine after radioactive iodine treatment

You may have stopped taking your thyroid hormone tablets in preparation for your treatment. Your nurse will tell you when you should start to take them again. Usually, this is 2 to 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.

The doctors will work out the correct dose for you and when to start taking it.

Radiation safety precautions

You will need to follow safety precautions for a few days after your radioactive iodine treatment. This is to protect others from the radiation. 

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

These precautions include:

Keeping your distance and avoiding close contact with people

Stay away from crowded places and avoid using public transport. If you live or work with other people, you will need to keep a distance from them. Avoid standing or sitting close to them. This stops them from getting radiation from you. 

Your doctor will tell you not to have close, lengthy contact with others for a couple of weeks. This includes babies, young children, pets and pregnant women. Avoid hugging and kissing other people.

Not sharing a bed

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.

Avoiding sexual contact

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. 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.

Practicing good hygiene

A small amount of radiation will still be in your sweat, urine and saliva. For a few weeks you will need to use your own towel and keep your cutlery and plates away from others until washed. Continue to flush the toilet twice and wash your hands thoroughly after using the toilet.

Travelling after radioactive iodine treatment

Recent treatment with radioactive iodine may set off radiation alarms at airports. Talk to you doctor if you plan to travel abroad. You can have a certificate from the hospital, or a letter from your doctor, explaining 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:

Inflammation of the salivary glands

Your salivary glands can become inflamed after treatment. This can cause symptoms such as swelling and pain. You can have painkillers to help with the inflammation.

Dry mouth

You may make less saliva (spit) and feel like your mouth is dry. 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. Some doctors recommend that you chew gum or suck sweets to keep the salivary glands working. If you have a dry mouth, you could try using artificial saliva to see if this helps. Your doctor or nurse can arrange this for you.

Changes to your taste

You may 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.

A swollen or tender neck and feeling flushed

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.

Feeling sick (nausea)

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:

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

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. Doctors feel that there is less risk of the radiation affecting a pregnancy after this time.

For a few people, inflammation of the salivary glands 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 sometimes affect the lacrimal glands. These are glands in your eyes which make tears. Rarely, some people develop dry eyes and 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. Radioactive iodine treatment can sometime affect the bone marrow. This can cause a small drop in the number of blood cells. This usually doesn’t last long and should cause no problems. As well as radioactive iodine you might have external radiotherapy if the cancer has spread to the bones. Having both treatments can cause a drop in the number of blood cells. If this happens you may have lower resistance to infection, 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 it 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

Some people might 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: 
24 May 2021
Next review due: 
27 May 2024
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