Treatment with Iodine-131 (I-131) for Thyroid Cancer

Patient Experience

  • Reference Number: HEY1102/2020
  • Departments: Nuclear Medicine
  • Last Updated: 28 February 2020


This leaflet has been produced to give you general information about your treatment.  Most of your questions should be answered by this leaflet.  It is not intended to replace the discussion between you and the healthcare team, but may act as a starting point for discussion.  If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team.

What Is Iodine-131 (I-131)?

Iodine-131 (also known as I-131 or radio-iodine) is a radioactive form of the iodine we normally eat in our diets.  I-131 is used to treat the thyroid gland in patients with overactive thyroid glands or thyroid cancer. It is administered as a small capsule that you swallow with water.

Why do I need treatment with I-131?

The thyroid gland concentrates iodine from the blood and stores it there until it is used by the gland to make thyroid hormones.  If we administer radioactive I-131, the radiation emitted by the iodine will destroy the cells around it.  For this reason it is often used to destroy any remaining thyroid tissue or microscopic deposits of thyroid cancer after surgery to the thyroid gland.

I-131 can also be used to treat thyroid cancer that has returned.

Can there be any complications or risks?

Radioiodine is a very safe treatment but like everything in life, there may be a small degree of risk.  Your doctor will only prescribe this treatment if the benefits to you outweigh any potential risks.

Side effects with I-131 are uncommon. Some patients have reported that their mouth, throat or neck has become slightly swollen or sore.   Please let the nursing staff know if you experience any side effects as they can provide advice and may give you some medication to ease any discomfort.

Sometimes people find that their sense of taste is slightly altered but this usually improves several days or weeks after your treatment.  Citrus fruit sweets, which encourage the production of saliva, can often help but these should only be used 24 hours after you have taken your I-131 capsule.

Whilst there is no evidence of people being harmed from the radiation associated with this treatment, some people believe there is no such thing as a safe dose of radiation, no matter how small. Therefore, we use the minimum amount of radiation needed to treat you. However, the radiation could be harmful to an unborn baby so the treatment must not be given to patients who are pregnant. Radio iodine can also pass into breast milk; therefore the treatment is unsuitable for patients who are breastfeeding.

After you have had the therapy, we advise women to avoid conception for six months and men to avoid fathering children for four months.

If you think that you might be pregnant, if you are breast feeding , or if you are planning to have a child within the next six months, you must contact the nuclear medicine department as soon as possible before your appointment.

There are some radiation protection precautions you will need to follow for a period of time after your treatment.  These are detailed in the section below.  It is very important that, before you attend, you read these precautions, understand them and discuss them with anyone who may be affected by your treatment.  If you are unsure about any of the instructions, or if you have any questions, please contact the Nuclear Medicine Department to discuss them with a member of staff.

What precautions do I need to follow after the treatment?

Other people who come into contact with you will receive some radiation dose from being near to you or if they become contaminated with any of your bodily fluids. Whilst there is no evidence that exposure to these low levels of radiation causes any harm, it is a sensible precaution to keep radiation doses as low as we can. This can be achieved by following the precautions detailed below.

When you attend, you will receive a treatment record sheet giving the exact time period that you need to follow the precautions for.  We will ask you to carry this record sheet with you for up to 8 weeks.

The exact length of time for which you need to follow the precautions depends upon the amount of radio iodine prescribed for you.

For up to 24 days, we will ask you to:

Stay at least 1 metre from children under 5 and pregnant women.

  • It is not necessary to send young children to stay elsewhere providing you can keep your distance from them, perhaps by having a partner or other relative help with looking after them.

For up to 18 days, we will ask you to:

Stay at least 1 metre from adults and children over 5

  • This does NOT mean that you have to avoid completely other people; only to restrict the time you spend close to individuals.  This may require you not to sit next to someone (e.g. whilst watching television) for more than one hour per day.  You should not share the same bed with other people, including children.

Avoid non-essential medical or dental treatments

  • This means that non-urgent visits (such as a routine blood test or dental check-up) should be postponed.
  • You will be attending the nuclear medicine department for a follow-up scan a few days after your treatment; it is safe to keep this appointment.

Avoid public places of entertainment (such as pubs, restaurants or the cinema)

  • The purpose of this is to avoid long periods of contact with another person, for example when sitting next to the same person for a few hours at the cinema or in a restaurant.

For 7 days, we will ask you to take extra care with hygiene. For example:

Try to avoid any spill of urine when using the toilet. If any urine is spilt, wipe it up with a tissue immediately and flush it down the toilet. (Male patients should sit on the toilet rather than standing)

Flush the toilet twice after each use and wash your hands thoroughly.

  • Most of the radioiodine leaves your body in urine. Good toilet hygiene minimises the risk of other people becoming contaminated with this iodine.

Rinse the bathroom sink, and bath or shower thoroughly after use.

  • Small quantities of radio iodine may leave your body in sweat. Washing this away before other people use the bathroom minimises the risk of other people becoming contaminated with iodine.

Avoid food preparation that involves a lot of handling of food (e.g. baking).

Wash your hands before preparing food for others.

  • This is to remove any radioiodine that that could be on your hands due to sweat, and avoid the risk of this radio iodine entering the bodies of other people from eating food contaminated with radioiodine.

Do not share crockery, cutlery, toothbrushes, towels, or facecloths.

  • Small quantities of radio iodine may be present in your saliva. These precautions minimise the risk of this being passed on to other people.

No kissing or sexual contact

  • This is to avoid contaminating others with you bodily fluids which may contain small amounts of radioiodine.

What about my children – can I see them after the treatment?

If you can follow the precautions detailed above, it will be safe to see your children after your treatment. Providing you follow these precautions, there is no need to be concerned.

Can I drive myself home or travel by public transport?

You will be able to drive yourself to and from the hospital or have somebody drive you but there should be no more than one other person in the car with you on the way home.

You can travel home by public transport if you wish, but if you think you will spend more than 3 hours on a bus or train, please let us know in advance so that we can discuss this with you.

Do I need to take time off work after the treatment?

This depends on how much radio iodine has been prescribed for you and the type of work you do.

  • If you work with children or pregnant women, you may need to take up to 24 days off work.
  • If your work involves handling food, you will need to take 2 weeks off work.
  • If you do not work with children or pregnant women, and do not handle food, you can return to work the day after the treatment providing your work allows you to keep your distance from other people (at least 2 metres). If you regularly work in close contact (closer than 2 metres) with other adults, you may need to take up to 8 days off work.

Please contact the Nuclear Medicine Department if you need more specific advice about when you can return to work.

Please note that the Nuclear Medicine Department are unable to issue fit notes (previously known as sick notes). If you require one of these, please contact your doctor.

How do I prepare for the treatment?

Share the information in this leaflet with your partner and family (if you wish) so that they can be of help and support.  There may be information they need to know, especially if they are taking care of you following this treatment.

You may need to stop taking certain drugs for several days or weeks before your appointment or have some injections in preparation for the treatment. Your appointment letter will give further details of what is required.

You will need to follow a low iodine diet and avoid medications containing iodine for 2 weeks prior to the therapy.

See the separate leaflet ‘Thyroid Tests and Treatments: The Recommended Low Iodine Diet’ for advice.

On the day of the treatment, you will need to fast from early in the morning. You may drink as usual. Your appointment letter will give more details.

There is some information which we need in advance.  This is so we can plan your treatment.  Please call the Nuclear Medicine Department before your appointment if any of the following applies to you:

  1. You have any problems with controlling your bladder, for example, if you wear pads or have a catheter.
  2. You are unable to look after yourself (including washing, showering and dressing) in a single hospital room for up to 5 days without assistance from anyone else.
  3. You have had any X-ray procedures involving the use of contrast in the 8 weeks prior to your appointment date.
  4. You look after young children. (You will be asked to avoid close contact with children and pregnant women for up to 24 days after your treatment, young children may need a different carer).
  5. Your home is not connected to the mains drainage / sewer system (for example if you have a septic tank).
  6. You do not have a washing machine at home to wash your clothes following the treatment. Contaminated clothing cannot be washed at a public launderette.
  7. You live in a residential care home or nursing home.
  8. For female patients:
  1. If you are breast feeding or have been breast feeding anytime in the 8 weeks before your appointment date
  2. If there is any chance that you might be pregnant.

Where will I have my treatment?

You will be given your treatment in an isolation room which has been specially adapted for patients who have been administered radioactive medicines. This room is on Ward 31 in the Queen’s Centre for Oncology and Haematology at Castle Hill Hospital. The room is set-up to keep you as comfortable as possible during your stay.

As well as the standard hospital bed and equipment, the room has an en-suite shower and toilet, a small kitchen area with a kettle, sink, and refrigerator. The window in the room looks out over the valley to fields in the background.

There is a TV and radio in the room which are both free of charge and will receive the majority of free TV stations and non-digital radio stations.  There is also a portable DVD player which you may use to watch your own DVDs.

The room has a telephone which will receive in-coming calls.  The ward staff will be able to give you the number of this telephone to pass to your family and friends.  It will also allow you to contact the ward staff if you need anything whilst you are in the room.

Why do I need to stay in hospital?

Once you have had your treatment, both you and your bodily fluids will contain radioactive material.  This material will be emitting radiation similar to X-rays and as a result people around you could get a radiation dose that they do not need.

Almost all of the iodine will pass out of your body over the first few days after your treatment.  Most of the I-131 will pass out in your urine but some will be excreted in your sweat and saliva and it is very important that other people do not come into contact with this.

The treatment room has been set up in a way that limits the amount of radiation anyone can receive from you.  It is also easily cleaned so that our staff can remove the iodine from the surfaces and materials in the room before it is used for another patient.

What can I bring with me?

I-131 is excreted in sweat; therefore anything you touch can become contaminated and may be too radioactive for you to take home with you. Items that can go into the washing machine are safe to take home and we ask that you put these straight in the washing machine when you go home. Other items either need to be disposed of or stored in the hospital for several months before you can collect them.

We therefore ask that you only bring in the minimum of what you will need during your stay so that we do not have to dispose of or store large quantities of personal belongings. It is likely that we will need to dispose of your toiletries or any makeup that you bring, so please only bring tester or travel-sized bottles.  Razors and toothbrushes also get heavily contaminated so please use disposable versions rather than electric shavers or toothbrushes.

Please bring with you a supply of any regular medications you take to last up to 5 days. Do not bring more than you need because we may need to dispose of any remaining medication should it become contaminated with I-131.

Please do not bring electronic items such as mobile phones, tablets or laptops. These do become contaminated and you will not be able to take them home with you. Your family will be able to contact you by phone on the phone in the room.

You will need a clean set of clothing to travel home in.  This should be put in the wardrobe in the room and not touched until you are advised that you can go home.

Whilst you are in the room you will need to wear slippers or socks to avoid contaminating the floor.

What happens on the day of the treatment?

Your treatment will be performed by a medical physicist from the Nuclear Medicine Department. However, before your treatment can begin you must be booked into the ward by the ward staff. You will have some routine checks including blood pressure and heart rate; swabs will be taken to test that you are not carrying an infection such as MRSA (Methicillin-Resistant Streptococcal Aureus).  A small sample of your blood will also be taken so that we can test to see what your thyroid hormone levels are. If you are a female patient under the age of 55, we will need to test a sample of your urine to be sure that you are not pregnant. We will also ask the date of your last menstrual period.

Once these checks are complete, the medical physicist will discuss the treatment with you. You will be asked questions about you, your life and your family.  This is to make sure that it will be safe for you to have the treatment and so that we can give you the right advice about radiation protection after your treatment.  There are some precautions that you will need to follow after the treatment and these will be explained to you and any questions you have about the treatment will be answered.

Once these checks are completed and your questions are answered you will be given the I-131 capsule to swallow with some water. If any of your family or friends have accompanied you, they will need to leave before we give you the capsule. The capsule is similar in size and shape to an antibiotic capsule or a paracetamol tablet and has no taste.  It is important that you swallow the capsule whole and do not chew it.

After you have swallowed the capsule, you will need to remain in the room until the medical physicist advises you that you can go home.

We will ask that you do not have anything to eat for 1 hour after swallowing the capsule.

How long do I need to stay in hospital?

This varies significantly between patients, and depends on how quickly your body excretes I-131. It is possible that you could be in hospital for up to 4 nights. However, the majority of patients undergoing this treatment are in hospital for 2 – 3 nights and in some cases only 1 night is required.

One hour after you have swallowed the capsule, the medical physicist will measure the radiation dose rate at 1 metre from you. This measurement will then be repeated each day and used to determine when you can go home. We will keep you informed about the most likely day you can go home as we take these measurements.

Can I have visitors?

You may have visitors from the day after you receive your treatment, provided the visitors are over 18 years of age and not pregnant (or possibly pregnant). Visitors must:

  • Stay at least 2 metres from you (we ask that they sit on chairs near the door and you sit on the armchair near the window.
  • Wear gloves and overshoes (provided outside the room), removing and disposing of these when they leave.
  • Not eat and drink whilst in the room.
  • Stay for a maximum of 1 hour each day.

Your visitors may bring items in for you such as books, newspapers and food but they must not take anything out of the room.

What happens on the day I am discharged?

When it is time for you to be discharged, you will be asked to have a shower and to change into your clean going home clothes.  We will ask you to put any clothing you have worn during your stay into a bag and to dispose of any items you are happy to throw away (e.g. toothbrush, toiletries and magazines). We will then move you to the ward day room whilst we check your belongings for contamination with a sensitive radiation monitor.

Your clothing will need to be washed twice, separately from the rest of the laundry when you get home.  Some items may be too contaminated to let you take them home when you go. If these cannot be disposed of, we will need to store them for several months and will contact you when you can come to collect them from the hospital. We will never stop you using personal items like false teeth, glasses or walking sticks and there is no need to remove wedding rings.

When the medical physicist has finished checking all of your belongings they will bring them to you in the day room.  You will be given any instructions about your belongings or anything we need to store. We will give you instructions in writing about precautions you must follow when you go home. More information about these precautions are included later in this leaflet.

You will then need to wait in the day room until the ward staff advise you that you can leave. You must not go back into the treatment room from this point but you are free to use the public toilets on the ward.

What happens afterwards?

You should have an appointment to attend the nuclear medicine department for a whole body scan a few days after your treatment. Please let us know if you have not received this appointment with your appointment for your treatment. The results of this scan are sent to the Consultant who requested the treatment who will contact you if anything further is required.

Should you require further advice on the issues contained in this leaflet, please do not hesitate to contact the Nuclear Medicine Department (01482) 622125

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

We collect and use your information to provide you with care and treatment. As part of your care, information about you will be shared between members of a healthcare team, some of whom you may not meet. Your information may also be used to help train staff, to check the quality of our care, to manage and plan the health service, and to help with research. Wherever possible we use anonymous data.

We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.

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