Radioactive Iodine Treatment (RAI)

How RAI Works - A video for Patients and Families

Who qualifies for RAI treatment?

Radioactive Iodine treatment (RAI) is a unique form of treatment for the differentiated forms of thyroid cancer (papillary & follicular). It is not often used in patients who are at low risk for recurrence.  Generally speaking, low risk patients are those who had a singular cancerous nodule without 'aggressive features', are less than 45 years old, and have no family history of thyroid cancer. These patients may be defined as having Stage I thyroid cancer. For detailed information about staging thyroid cancer, view the 2015 ATA Guidelines.

Why RAI is used

The following information applies to those who have been advised to have RAI treatment by their doctor.

RAI treatment has two primary purposes: 

  • The treatment destroys any remaining thyroid cells (both normal and cancerous) and minimizes the risk of recurrence.  This is also known as ablation therapy.
  • Destroying any remaining normal or cancerous thyroid tissue left behind after the thyroidectomy surgery facilitates the use of a unique protein marker called Thyroglobulin (Tg) in the future. Tg is measured in blood tests.

In years past, a treatment dose of RAI was usually in the range of 3.7-5.5 GBq (100 or 150mCi).  More recently, and in keeping with the 2015 ATA Guidelines, it may be appropriate for a patient to have a dose of 30 or 50mCi of RAI.  Ask you doctor which dose is appropriate for you. It can vary based on the size or number of initial tumours, aggressive features of the pathology, and other risk factors. More recent research indicates that a lower dose, of 1.1 GBq (30mCi) may be as effective, with fewer potential after-effects.  If you require RAI, ask your doctor to discuss the dosage with you.

The initial RAI treatment may be given anytime, but is usually used sometime within six weeks to six months post-surgery.

Some specialists reverse the protocol. That is, they closely follow patients in the post-surgery months using ultrasound and blood tests (such as measuring Tg) and keep the radioactive iodine treatment an option if the test results indicate its necessity.

Approximately one week after having the RAI treatment, a nuclear scan known as a Whole Body Scan (WBS) is normally given.  The scan will indicate how much remnant tissue remains in the neck area following the surgery, and may indicate any metastases (spread) of the cancer to other parts of the body.

Preparing for RAI

One of the ways to maximize the uptake of the radioactive iodine is by stimulating the thyroid cells to take up the radioactive iodine by raising the TSH level.  There are 2 ways of achieving a high TSH level.  They include being withdrawn from hormone replacement (“going hypo”) or using Thyrogen®, a medication given by injection. Another part of the preparation is to go on a Low Iodine Diet.

Precautions and Isolation

"Going Hypo"

Our bodies require thyroid hormone (T4); a hormone taken in synthetic form (by a daily pill) once the thyroid has been removed.  The body also requires T3 which it converts from T4. Without thyroid hormone, the body produces an increasing amount of thyroid stimulating hormone (TSH).  An elevated TSH of at least 30 mIU/L is needed for the RAI treatment to be effective. To achieve this rise in TSH, patients may be instructed to stop taking their thyroid hormone replacement pills.

Becoming hypothyroid by hormone withdrawal, involves stopping levothyroxine (L-T4; the drug’s brand names in Canada are Synthroid and Eltroxin) for approximately 4-6 weeks prior to RAI treatment.  During the time that levothyroxine is not taken, Cytomel (L-T3) may be prescribed. Cytomel is a fast-acting (and fast dissipating) form of thyroid hormone used to minimize the symptoms of hypothyroidism during hormone withdrawal. Cytomel is stopped approximately 2 weeks prior to RAI treatment.

‘Going hypo’ is a gradual process with symptoms (if any) increasing slowly over the six week period. The longer the patient is off of thyroid hormone, especially during the last two weeks prior to RAI treatment when no thyroid hormone is taken, the more likely the patient will experience symptoms of hypothyroidism.

Some Symptoms Associated with Hypothyroidism:

  • Tiredness, loss of energy, weakness
  • Trouble sleeping, nightmares or excess sleep
  • Puffiness especially in the face and bloating
  • Loss of ability to concentrate, memory loss, absentmindedness
  • Weight gain
  • Anxiety, panic attacks, irritability, mood swings
  • Depression
  • Dry eyes, skin and hair; hair loss
  • Change in menstrual cycle
  • Joint pains and stiffness, muscle cramps
  • Intolerance to cold
  • Constipation and/or nausea
  • Tingling or numbness in fingers or toes
  • Itchiness
  • Ringing in ears
  • Slight changes in eyesight


As an alternative to a patient ‘going hypo’, doctors have the option of effectively raising the TSH level by giving the patient TSH in the form of Thyrogen® (rhTSH) to prepare patients for RAI treatment. In that case, the patient does not withdraw from their thyroid hormone but continues taking their daily dose of L-T4 each day.  They do not become ‘hypo’ or have associated symptoms. This form of preparation for RAI treatment is known as ‘TSH stimulated’. When taking Thyrogen® in preparation for RAI treatment it is not necessary to have a measured TSH of at least 30 mIU/L as it is during the hypo or ‘withdrawal preparation’.

Thyrogen® is fast-acting and fast-dissipating and requires two visits to a doctor (or other clinician) as it is given by injections.  Most patients have mild (if any) side effects from Thyrogen® and avoid hypothyroid symptoms described above. If Thyrogen® is selected, patients will need to get the injections on the 2 days just prior to the RAI treatment. 

For detailed product information about Thyrogen® including side effects and reactions, contra-indications, special information regarding the dosage (such as those for pregnant women or children), click here.

To view the typical schedule for injections of Thyrogen®, click here.

In some Canadian provinces, the cost of Thyrogen® is not covered by the provincial medical/drug programs, nor by local hospital formulary programs. In other provinces, the cost of Thyrogen® is covered. Where the costs are not covered, patients must pay for it themselves or apply to their private health insurance for full or partial coverage. 

Some provinces also have drug programs available which are related to income level needs. For those who pay out of pocket, the current cost for the two injections of Thyrogen® that come within one kit, is approximately $1,800 or more.  

Patients should be aware that the Thyrogen® kit does not include sterile water, which is a necessary component of the injection. Patients should be sure to pick up sterile water at the pharmacy with their prescription of Thyrogen®. Pharmacies charge up to $10 for the water.

Other resources for Thyrogen®

About the Low Iodine Diet

To ensure that absorption of the radioactive iodine is maximized, patients should reduce the dietary intake of iodine prior to the use of RAI.  This can be achieved through a Low Iodine Diet (LID)

Information about Staging and Recurrence

What's New

More details about the above HERE

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