Radioactive Iodine-131 is an effective and safe form of therapy to treat thyrotoxicosis and toxic nodules in the thyroid gland.

Why is Iodine-131 used?

A normal thyroid gland uses iodine from your food to produce thyroid hormone.  The radioactive form of iodine, I-131, accumulates in the thyroid gland in the same way.  The radiation given off by the I-131 is localised to the thyroid and reduces the function of the over-active thyroid cells which is the purpose of this treatment.


You may need to stop taking certain medications that would affect the uptake of iodine by your thyroid.  Please check your medications with your doctor at the time the appointment is made.

You will be asked to attend a consultation with one of our physicians 7 days prior to therapy. If you are a female of child-bearing age, you are required to obtain a blood test after the initial consultation to confirm that you are not pregnant.  You must then take appropriate contraceptive measures to ensure that you do not become pregnant from that time until 6 months after receiving the I-131 therapy.  A second blood test will be performed on the morning of the therapy, and your iodine therapy will be given to you pending these results.

How is the I-131 given?

When you arrive in the Nuclear Medicine Department, staff will check that the treatment request from your doctor is accurate and explain the procedure to you.  The I-131 is given in the form of a capsule.  You will be handed the capsule in a dish, together with a cup of water.  Wearing gloves, you must swallow the capsule whole and wash it down with the water.  DO NOT CHEW THE CAPSULE – IT MUST BE SWALLOWED WHOLE.

How you will feel

You should not experience any side effects from the I-131 therapy.

Precautions when you return home

The amount of I-131 that you receive is determined to produce the desired therapeutic effect while minimising the radiation exposure to your family and friends.  However, after you have received the capsule you will be emitting some radiation.  The I-131 is excreted from your body in your urine and in your saliva.

To ensure that there is minimal risk to your family and friends there are a number of precautions that must be followed. The time for these restrictions varies from patient to patient.  The Nuclear Medicine Physician will discuss your particular situation with you and will inform you how long you should follow these instructions (i.e. the ‘restriction period’):

What are the most important precautions to minimise radiation to others?

The most important factors are distance and time. Try to maintain a distance of at least 1 metre from other people. Do not sit or stay close to any person either at home or at work. If you are with someone for longer periods (perhaps more than one hour), stay at least 2 metres away.

Passing someone briefly, for example in the street, or while shopping, is permissible - as is a quick hug.

What about contacts with pregnant women?

Contact with pregnant women should be minimised. Try to stay at least 2 metres away from a pregnant woman.

Can I still see my children and care for them?

If your children are under five years old, minimise hugging or holding and avoid prolonged contact for the specified restriction period.

What about infants?

Children under three years old should be looked after by someone else. If possible, arrange for them to stay with relatives or friends.

Can I be in close contact with my partner or other people at home?

You should sleep in a separate bed and restrict sexual contact for the specified restriction period. Beds should be at least 2 metres apart, even if there is a wall separating them. This is because the walls of a house do not provide good protection against the type of radiation emitted by iodine-131. Kissing should be avoided in order to prevent the transmission of radioactivity in the saliva.

What if my partner is pregnant?

If your partner is pregnant, it is important to avoid close contact with her.

Do these precautions apply for contact with people over 60 years of age?

The radiation related risk is much lower for people over 60 years of age than it is for younger people. For that reason, special precautions are less important.

Can I receive visitors?

Short visits, less than two hours, create no problem. Keep at a distance of about 2 metres and preferably avoid close contact. You should discourage visits by young children and pregnant women.

Can I go to work?

Most people can go to work. If, by the nature of your work, you are within 1 metre of the same individual(s) for more than two hours per day, you should seek advice from your doctor.

What if I am a nursery school teacher?

Nursery school teachers, or others who are in close contact with young children during working hours, should stay off work. Your doctor will indicate the required period of time for this restriction.

Can I go to the movies or other entertainment?

Avoid visiting cinemas and other social events for the first 2 days where you are close to other people for more than one hour.


May I use public transport?

Public transport can involve you sitting close to another person and restrictions may be required on travel of long duration. For long trips you should try to find a place where you can sit alone. Long distance travel immediately after administration is not recommended due to the potential for travel sickness and the possibility for contamination. Your doctor will advise you on appropriate travel times.

What about using a taxi?

Sit in the back on the opposite side from the driver. Do not spend more than two hours with any one taxi driver.

Can I use the same toilet as other people?

Yes, but spilling of urine needs to be avoided. Therefore, (also for men) pass urine while seated. Always dry your genitals with toilet paper and flush the toilet. It is also important to wash your hands immediately afterwards, even when only urinating.

What about cutlery, crockery, bed linen, towels etc.?

Radioactive iodine also leaves the body in the saliva and the sweat of patients. Therefore, cutlery, crockery, towels, bed linen etc. should not be shared with others. After washing they are completely safe. There is no need to wash them separately.

What happens if I have to go to hospital?

If you have to go to hospital unexpectedly, please inform the doctor that you have been treated with radioactive iodine recently. This applies even when it is the same hospital where you were treated.

Will it affect my ability to have children?

No.  For both females and males, fertility is not impaired by this therapy.

When is it safe to become pregnant / father children?

Some of the radioactive iodine will remain in your body for several months and it is recommended that females should avoid becoming pregnant for six months and males should not father children for four months following the treatment.

What happens if I have to go overseas?

Some airports, as part of their security, have extremely sensitive radiation detectors that are able to detect minute amounts of radioactivity. If you will be travelling by air within 2 months of your treatment you should take some documentation about your treatment. Your doctor can provide this for you.



9716 3600


 8042 3000


9911 6800

Five Dock

8705 8300


9598 0100


8228 9000

North Strathfield

8282 8100

North Sydney (Mater Imaging)

9955 4466
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