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 Iodine 131

Therapeutic Treatment of Hyperthyroidism
 (Overactive Thyroid)


The best source of information on your radioactive iodine treatment is your ordering doctor. He/She will be able to answer any questions you may have about your situation. This pamphlet serves as a general informational tool. It contains special instructions for you to follow when you go home after your treatment.

You or a member of your family has been given Iodine-131 that is a radioactive drug, for the Therapeutic Treatment of Hyperthyroidism (Overactive thyroid).

You and your doctor have agreed it is the most appropriate treatment for your thyroid condition.  The radiation from the radioiodine will be absorbed by your thyroid gland and will interfere with the function of the thyroid cells.  This is the desired and beneficial medical effect of the treatment.

Your body will get rid of most of the Iodine-131 during the next two (2) days, primarily in your urine and to a lesser extent in your saliva.  As a result of this normal process your urine and saliva will be radioactive.  Additionally, the radiation given off by the Iodine-131 will be leaving your body at all points without you or others knowing it.

Because this drug is radioactive, it is extremely important that you make the following temporary changes in your behaviour.  This will limit the radiation exposure to both you and those people with whom you may live and/or work.

You must STOP breast feeding for at least 6-8 weeks prior to getting the capsule. A portion of the radioactive material will appear in your breast milk.  If you continue to breast feed, your child will receive unnecessary radiation exposure and potential damage to their thyroid gland. We do not treat breastfeeding mothers.

Except for breast-feeding, the risk associated with this radiation exposure is very small if the guideline and precaution instructions are followed.  The basic point to remember is that you, as the patient need the radiation, others don’t.


  1. DISTANCE – the greater the distance you are from others, the less radiation they will receive,
  2. TIME – the less time you spend around others, the less radiation exposure they will receive,
    Use both of these points together and
    treat others as if you have the flu!!
  3. HYGIENE – good personal hygiene habits are essential to lower the possibility of transferring Iodine-131 to others.

If you are travelling by air or by car within the next two months, please ask for a travel letter from the nuclear medicine department.

If you are pregnant, or think you could be, tell your doctor because the radioiodine treatment should not be given during pregnancy.


Precaution - activities Time
Avoid kissing 2 Days
Avoid sharing items (ie food/drinks) that contact the mouth 2 Days
Use separate/disposable eating utensils 2 Days
Drink plenty of fluids 2 Days
Suck on sour candy 2 Days
Men must sit during urination 2 Days
Flush the toilet 2 extra times after each use with the lid closed 2 Days
Wash hands frequently, also after using the toilet 2 Days
Use separate towels and washcloths 2 Days
Wash underclothes separately 2 Days
Bathe or shower twice daily 2 Days
Breast Feeding STOP
If your sleeping partner is pregnant or a child sleeps in your bed,  sleep separately for 17 - 22 days ***
If you must hold an infant or child for more than 30 minutes per day wait 15 - 20 days ***
Sleep alone in separate bed (2m separation) varies - ask your nuclear medicine technologist.
*Avoid contact with pregnant individuals 1 - 5 days ***
* Avoid contact with young children 1 - 5 days ***
Maintain prudent distance from others (2m) 1 - 4 days ***
**You may return to work after (maintain 1m separation) 1 - 5 days ***
Limit time spent in public places 1 - 4 days ***
Avoid using mass transportation (ie airplanes, bus or trains) for 1 - 4 days ***
Private prolonged car trips with others (1m separation) 4 days
Prevent pregnancy (female) 6 months
Prevent pregnancy (male) 4 months
Patient hospitalization Inform your nurse and doctor that you have received radioactive I-131.

*  Every attempt should be made to stay at least 3m away from children or pregnant women most of the time and no closer  than  1m  for brief periods of time only (i.e. a few minutes)

** The majority of people can return to work. If, by the nature of your work you are within 1m of the same individual(s) for a significant part of the day, additional restrictions may be necessary. Nursery school teachers or others who are in close contact with young children during work hours may also require an extension of the precautionary period. Precautions will be determined on an individual basis.

*** Varies depending on amount of medication you receive for your treatment.

Ask Your Doctor

Do not hesitate to talk to your Doctor or the Nuclear Medicine Department about your treatment. All medical questions should be directed to your Physician.

Ask the Radiation Safety Officer

If you have any questions concerning your treatment

Christopher Lyn BSc, MRT(N)
Radiation Safety Officer for CVH
(905) 813- 1100 ext. 4483

Collin Lewis BSc, MRT(N), CNMT
Radiation Safety Officer for MH and QHC
(905) 848-7580 ext. 3547 or 5646

Nuclear Medicine Department