What are the possible side effects from radioiodine?
Information booklet about your treatment for
thyroid cancer using radioiodine
This leaflet provides information about your treatment with
radioiodine. It explains what this treatment is and how it is
given. It also answers some of the most common questions
people ask about this treatment. If any of the information is
not clear or if you have questions not answered by this
leaflet, then please ring the Department of Nuclear Medicine
on 02920 316237.
What is radioiodine?
Radioiodine is a radioactive form of iodine. Iodine is part of
each of our diets and is needed for the thyroid gland to work
What does the thyroid gland do?
The thyroid gland controls the speed (metabolic rate) at
which our body works.
How does radioiodine work?
Like ordinary iodine, radioiodine is taken up by any thyroid
cells left after your thyroid operation. The radioactive form of
iodine is used to destroy any remaining thyroid cells.
How do you know if I need treatment?
The doctor may recommend that you have a radioiodine
scan to help plan your radioiodine treatment.
Is a radioiodine scan always done?
No. In some cases it is not necessary to do the radioiodine
scan and you may be advised to have radioiodine treatment
based on the information known from your operation.
Only a low dose of radioiodine is needed to carry out a
radioiodine scan. This can be given to you as an outpatient
and is usually in a capsule form.
If I am advised I need it, where will my radioiodine
therapy be done?
If you are advised to have radioiodine therapy you will need
to be admitted to the isotope cubicle.
This is a single room with a bathroom on the Princess
Margaret Ward, Velindre Hospital. This room has been
specially adapted because of the high dose of radiation
involved in treatment. The treatment dose of radioiodine is
also given as a capsule.
I have been told I will need to stop my thyroid tablets
before my radioiodine, why is this?
Thyroid hormone tablets interfere with the radioiodine
treatment. We will ask you to stop taking these tablets
before and during your treatment to make sure the thyroid
cells left in your body take up the radioiodine. These tablets
include T4 (thyroxine) and T3 (Tri-iodothyronine).
Are there any side effects associated with stopping the
You may feel tired or weak when not taking these tablets.
This is normal and the effects will disappear once you start
taking them again.
When do I start taking the thyroid hormone tablets
If you have the treatment dose you will usually start taking
your tablets again on the day you leave the ward.
If you don’t need a treatment dose you will usually start
taking your tablets again on the day we get the results from
the initial test of you thyroid.
What are the possible side effects from radioiodine?
Many patients do not experience any side effects with
radioiodine. However the following side effects can occur;
• dry mouth
• tender or swollen saliva glands
• taste changes
• sore throat
• altered sensations around your thyroidectomy scar
• swelling of your thyroid area if a significant amount of
thyroid tissue is present
• feeling sick (this is uncommon)
Can I have the treatment if I am pregnant?
No. We will ask if you are pregnant before we give you the
radioiodine capsule. If there is any doubt then a pregnancy
test will be done.
You will need to avoid becoming pregnant for six months
after your radioiodine treatment.
Can I father a child?
You will be advised to avoid fathering a child for four months
after your treatment.
Can I eat and drink as normal before I have the
We encourage you to drink plenty of fluids, as this will help
clear the radioactivity from your body more quickly. The
doctor will ask you to cut down on certain foods that contain
significant amounts of iodine for seven days before you
receive your radioiodine. Your doctor will discuss this with
you in clinic. We will give you a diet sheet to help.
Is radioiodine dangerous to others?
We try and keep unnecessary radiation exposure to others
to a minimum. We will advise you on how to achieve this
with your family and friends.
Staff will not stay with you for any longer than is necessary
to attend to your needs. Staff will also wear gloves and other
special clothing whilst in your room on the ward.
What happens if I have to come as an outpatient for the
initial thyroid scan?
You will have an appointment at Velindre Hospital’s
outpatient department. The doctor will explain the
investigation and possible treatment plans. You will have the
chance to ask any questions you may have. We will ask you
to sign a consent form. Then you will have a blood test.
On the following Monday the physicist will give you the
radioiodine capsule in the Nuclear Medicine department.
We will explain everything to you and will also give you a
letter explaining the things you need to do afterwards.
We usually ask you to come back to the Nuclear Medicine
department three days later. This time you will have a scan
and we will measure the amount of radioactivity in the area
of the thyroid gland. This simply involves you lying down on
a bed for the scan and sitting on a chair for the neck
When will I know the results of the scan and
As soon as possible, once the doctor has seen them. He or
she will then decide whether you need to have radioiodine
treatment as an in-patient. If this is recommended, we
usually ask you to come into hospital the following week.
What happens if I have to come in as an in-patient?
You need to go to Princess Margaret ward. You will be seen
by the ward doctor, a nurse and a physicist. They will take
some details from you, then take you to the isotope cubicle.
The physicist will come to the cubicle and give you the
radioiodine treatment capsule.
After an hour the physicist will come back to the cubicle to
measure the level of radiation inside of you. We will ask you
to lie on the bed while a special monitor inside the cubicle
does this. This will be repeated each day. The measurement
does not hurt you.
How long will I be in the hospital?
Most people are in hospital for three to four days. Whilst you
are in the cubicle we will ask you to drink as much as
possible. This helps flush the remaining radioactivity out of
your body. Once the radioactivity level in your body is low
enough you will be able to go home.
Does anything else need to be done before I go home?
Before you go home you will be taken to the Nuclear
Medicine department for a scan. We will ask you to shower
and change into some clothing that you have not worn
during your stay in the cubicle.
The scan is in two parts. Each part takes about 30 minutes
and looks at where the radioiodine has gone into your body.
You have to follow some instructions after leaving hospital,
but we will explian these to you.
What happens to the clothing I have worn whilst in the
You can either leave it in the cubicle for us to dispose of, or
you need to wash it separately from everyone else’s when
you go home.
Can I have visitors whilst in the isolation cubicle?
You can have visitors but unfortunately children, pregnant
women or breast-feeding women cannot visit you whilst in
the isolation cubicle.
Other visitors will not be allowed to come into your cubicle
but you can speak to them via a phone in your room and
another in the corridor. You will be able to see each other
through a special window whilst you are talking. All visitors
must speak to the ward staff before they visit.
What can I do to help?
• When washing, and particularly when brushing your
teeth, please take care not to splash the water outside
the hand basin.
• Rinse your toothbrush thoroughly after each use.
• Take care not to splash urine outside the toilet pan and
flush the toilet twice after use.
• If possible take a daily shower.
What things do I need to bring in with me?
• Washing items for example towel, soap, toothbrush,
toothpaste, shaving kit, hair brush or comb. Please
bring small travel size bottles as we suggest you leave
all unused toiletries in the cubicle when you go home.
• Several changes of clothing
• Magazines and paperback books. Please do not bring
in hardback or library books.
• Soft drinks (small bottles 650mls or cans)
You should also bring enough money to pay for any
newspapers or phone calls you may wish to make. The
money for any newspapers will be collected before you go
into the cubicle.
You can take money into the isotope cubicle for any phone
calls you might wish to make. There is a telephone in your
room which will take incoming calls. We will give you the
extension number when you come in. Your family and
friends will be able to contact you via the main switchboard
on 029 2061 5888 then ask for your extension number.
What facilities does the isotope cubicle have?
As well as the usual furniture, the isotope cubicle has the
• A small fridge
• TV / DVD
• Radio / CD player / clock
We ask that you do not bring your own electrical items into
the hospital if possible. This is because we have to check
them for safety.
Will I have to have another treatment?
You will have a clinic appointment a few weeks after your
treatment. The doctor will examine you, and discuss the
scan that you had whilst you were an in-patient.
Some patients will need further treatment doses of
radioactive iodine. We will discuss any need for further
scans and treatment with you in out-patients.
We hope you have found this leaflet helpful. If you have any
questions or want further information, please phone the
Department of Nuclear Medicine on 029 2031 6237.
Velindre Cancer Centre
Phone: 029 2061 5888
This leaflet was written by health professionals. The
information contained in this leaflet is evidence based. It is
reviewed and updated every 2 years.
Written December 2003
Reviewed June 2009