Home > Patients & Visitors > Health Library > Radioactive Iodine
Radioactive iodine, given in a capsule or liquid form,
is absorbed and concentrated by the
thyroid gland. The treatment destroys thyroid tissue
but does not harm other tissue in the body.
See a picture of the
While radiation can cause
thyroid cancer, treatment of
hyperthyroidism with radioactive iodine does not
increase your chances of getting thyroid cancer.
Within days, the radioactive iodine
passes out of your body in your urine and saliva. How long it takes will depend on the dose you received and your age. Young people get rid of radioactive iodine faster than older adults.
Most people don't feel different after treatment. But a few people may feel a little nauseated.
Your doctor will give you written instructions. To avoid exposing other
people to radioactivity, it is important to follow your doctor's instructions carefully. He or she will instruct you on how far to stay away from people, how long you need to sleep alone, and other ways to stay safe. You will be directed to avoid
close contact, kissing, sex, and sharing cups, dishes, or utensils.
Some general recommendations include:footnote 1
Radioactive iodine may be used to
treat hyperthyroidism in people who have noncancerous (benign) thyroid nodules
that make too much
Radioactive iodine is
also used if you have your thyroid removed (thyroidectomy) because of thyroid
cancer. Radioactive iodine therapy destroys any remaining thyroid tissue or
cancer cells that were not removed during surgery.
In almost all cases, your thyroid
hormone levels will return to normal or below normal after radioactive iodine
treatment. This may take 8 to 12 weeks or longer. If your thyroid hormone level
does not go down after 6 months, you may need another dose of radioactive
If you have thyroid cancer and you are treated with
radioactive iodine, it may take from several weeks to many months for your body
to get rid of any remaining cancer cells.
Your thyroid nodule is
unlikely to grow after being treated with radioactive iodine.
The risks from radioactive iodine treatment
If you are pregnant, you should
not receive radioactive iodine treatment. This kind of treatment can damage
your fetus's thyroid gland or expose your fetus to radioactivity.
You should not breastfeed your baby after you have been treated with
radioactive iodine. Ask your doctor when it is safe to breastfeed.
people with thyroid cancer will receive different doses of radioactive iodine.
If you are young and you do not have a great risk of your cancer coming back,
you will probably need less radioactive iodine than an older person. Sometimes
this means that a younger person who receives radioactive iodine treatment will
not have to stay overnight in a hospital.
Traveling after treatment
If you have had
radioactive iodine treatment and you want to travel 3 to 4 days after
treatment, it is important to prepare for any problems you may have at airport
security. People who have had radioactive iodine treatment can set off the
radiation detection machines in airports for a week to 10 days.
Complete the special treatment information form (PDF)(What is a PDF document?) to help you understand this treatment.
Sisson JC, et al. (2011). Radiation safety in the treatment of patients with thyroid diseases by radioiodine 131I: Practice recommendations of the American Thyroid Association. From the American Thyroid Association Taskforce on Radioiodine Safety. Thyroid, 21(4): 335–346.
ByHealthwise StaffPrimary Medical ReviewerE. Gregory Thompson, MD - Internal MedicineSpecialist Medical ReviewerMatthew I. Kim, MD - Endocrinology
Current as ofNovember 20, 2015
Current as of:
November 20, 2015
E. Gregory Thompson, MD - Internal Medicine & Matthew I. Kim, MD - Endocrinology
To learn more about Healthwise, visit Healthwise.org.
© 1995-2016 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
Our interactive Decision Points guide you through making key health decisions by combining medical information with your personal information.
You'll find Decision Points to help you answer questions about:
Get started learning more about your health!
Our Interactive Tools can help you make smart decisions for a healthier life. You'll find personal calculators and tools for health and fitness, lifestyle checkups and pregnancy.
Feeling under the weather?
Use our interactive symptom checker to evaluate your symptoms and determine appropriate action or treatment.