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Radio-iodine (I-131) Treatment

Radio-iodine (I-131) Treatment: Overview, Procedure, Where to Seek Treatment | Singapore General Hospital

Radio-iodine (I-131) Treatment - What it is

This procedure treats the condition Thyrotoxicosis.

The thyroid gland requires iodine to manufacture thyroid hormone. Iodine comes from the food that we take and some foods are especially rich in iodine e.g. seafood.

Thyrotoxicosis is a condition where the thyroid gland is overly active. This condition can be treated by giving radioactive iodine by mouth. The radio-iodine is processed by the thyroid in the same manner as the iodine from food. The radiation given off by the radio-iodine reduces the function of the thyroid cells and inhibits their ability to grow, which is the desired medical effect. The amount of radio-iodine given is dependent on the patient's medical condition. The dose is decided by the Nuclear Medicine physician after he has conducted a series of tests on the patient. The dosage may not be the same for every patient.

In some cases, a second dose of iodine might be required if the first dose is not effective.


The radio-iodine is a colourless and tasteless liquid, just like water. It is kept in a small plastic tube in a lead container. You will be told to drink the radio-iodine using a short straw. Be sure to drink every drop to ensure accuracy of the dosage given. After you have drunk the radio-iodine, some water will be added to the tube and you are to drink the water as well.

Before Treatment

If you are pregnant, or think you are, tell your doctor because radio-iodine should not be given during pregnancy.

Avoid the following foods three days before till three days after treatment:

  • Seafood (including canned food) e.g. crabs, squids, oysters, cockles, prawns, seaweed.
  • Tea
  • Lemonade
  • Cola
  • Pizzas

Keep your stomach empty two hours before the treatment. Stop all anti-thyroid drugs, cough mixtures, multi-vitamins and traditional herbal medicine three days before till three days after the treatment. Stop L-thyroxine (thyroid medication) for four weeks before the treatment.

After Treatment

  • You should avoid pregnancy for the next six months.
  • If you have been breastfeeding your baby, you must stop because radio-iodine is secreted in breast milk. You can resume breastfeeding after one month.
  • Avoid close contact with individuals (especially children and pregnant women) for 3 days as they may be exposed to small amount of radiation. There is no evidence that such exposure causes harm, but efforts should be made to avoid unnecessary exposure to radiation.
  • You will be advised by the doctor whether to continue the anti-thyroid medication after the treatment. Thyroid Cancer Treatment The procedure and patient preparation are the same as for thyrotoxicosis. The only difference is that you will be given a much higher dosage of radio-iodine. This will enable the thyroid cells to be killed. You will have to be hospitalised for up to four days for this treatment. This is because your body wastes will be radioactive and they have to be stored in special holding tanks where they are allowed to remain until they are less radioactive before they are flushed into the normal sewers. You should not have any visitors during your stay in the ward to avoid unnecessary radiation exposure to them.

Radio-iodine (I-131) Treatment - Symptoms

Radio-iodine (I-131) Treatment - How to prevent?

Radio-iodine (I-131) Treatment - Causes and Risk Factors

Radio-iodine (I-131) Treatment - Diagnosis

Radio-iodine (I-131) Treatment - Treatments

Radio-iodine (I-131) Treatment - Preparing for surgery

Radio-iodine (I-131) Treatment - Post-surgery care

Radio-iodine (I-131) Treatment - Other Information