Potassium iodate 

Potassium iodate is a thyroid blocking medicine. It is given before a particular type of isotope scan at Great Ormond Street Hospital (GOSH) called a MIBG scan. The potassium iodate protects the thyroid against the isotope given during this scan.

How is potassium iodate given?

Potassium iodate is given by mouth in the form of tablets. They can be swallowed whole with water or crushed and mixed with milk, juice or yoghurt. We have produced a short video showing how to give your child tablets which you can watch on our website or on the GOSH YouTube channel.

To prepare for the MIBG scan, your child will take three doses of potassium iodate in all and it is vital that your child takes all three doses.

  • „„Dose 1 – at lunchtime on the day before the injection.
  • „„Dose 2 – at lunchtime on injection day (before or after the injection).
  • „„Dose 3 – at lunchtime on scan day (before or after the scan). 

Who should not take potassium iodate?

People with the following conditions should discuss using potassium iodate with their doctor.

  • „„Hypersensitivity to potassium iodate or any of its ingredients.
  • „„Hypersensitivity to iodine. 
  • „„Pregnant, could be pregnant or trying to become pregnant.
  • „„Existing kidney disease. 
  • „„Existing thyroid problems.
  • „„Certain itchy skin diseases especially dermatitis herpetiformis.
  • „„Certain types of vasculitis (blood vessel inflammation). 

What are the side effects?

Very rarely, children receiving potassium iodate have an allergic reaction. This reaction may be mild to severe. Signs of a mild allergic reaction include skin rashes and itching, high temperature, shivering, redness of the face, a feeling of dizziness or a headache. Signs of a severe allergic reaction include any of the above, as well as shortness of breath or chest pain.

Other side effects are more likely when potassium iodate is taken at high doses or for a long period of time so are unlikely with the short course required before an MIBG scan.

Interactions with other medicines

Some medicines can react with potassium iodate, altering how well it works. Always check with your doctor or pharmacist before giving your child any other medicine, including medicines on prescription from your family doctor (GP), medicines bought from a pharmacy (chemist) or any herbal or complementary medicines. The following are known to react with potassium iodate:

Important information

  • „„Always check the expiry date of the medicine before you give it to your child.
  • „„Keep medicines in a safe place where children cannot reach them.
  • „„The tablets should be kept in their original packaging in a cool, dry place out of direct sunlight and heat.
  • „„If your child vomits straight after taking the dose, inform your local doctor or nurse, as your child may need to take another one.
  • „„If your doctor decides to stop treatment or the tablets pass their expiry date, return any unused tablets to the pharmacist. Do not flush them down the toilet or throw it away. 

You should read this information sheet in conjunction with any patient information leaflet provided by the manufacturer. However, please note that this information explains about the use of potassium iodate in children and young people so may differ from the manufacturer’s information.

Each person reacts differently to medicines, so your child will not necessarily suffer any side effects mentioned. If you have any questions or concerns, please ask your doctor, nurse or pharmacist.

Compiled by: 
The Pharmacy Department in collaboration with the Child and Family Information Group.
Last review date: 
January 2014


Please read this information sheet from GOSH alongside the patient information leaflet (PIL) provided by the manufacturer. If you do not have a copy of the manufacturer’s patient information leaflet please talk to your pharmacist. A few products do not have a marketing authorisation (licence) as a medicine and therefore there is no PIL.

For children in particular, there may be conflicts of information between the manufacturer’s patient information leaflet (PIL) and guidance provided by GOSH and other healthcare providers. For example, some manufacturers may recommend, in the patient information leaflet, that a medicine is not given to children aged under 12 years. In most cases, this is because the manufacturer will recruit adults to clinical trials in the first instance and therefore the initial marketing authorisation (licence) only covers adults and older children.  

For new medicines, the manufacturer then has to recruit children and newborns into trials (unless the medicine is not going to be used in children and newborns) and subsequently amend the PIL with the approved information. Older medicines may have been used effectively for many years in children without problems but the manufacturer has not been required to collect data and amend the licence. This does not mean that it is unsafe for children and young people to be prescribed such a medicine ‘off-licence/off-label’. However, if you are concerned about any conflicts of information, please discuss with your doctor, nurse or pharmacist.