The low iodine diet (LID) is recommended for people who will be treated with radioactive iodine (RAI) for thyroid cancer.

If you are undergoing RAI to treat hyperthyroidism, you are not required to follow a LID unless you have been asked to do so by your doctor or medical team.

This information leaflet explains the reasons for trying to avoid foods that are high in iodine and suggests low iodine foods that you can eat. 

Low iodine fact sheet

Why follow a LID?

Research suggests that a diet which is high in iodine may affect the results of your RAI treatment. The purpose of the LID is to reduce the amount of iodine in your body before your treatment begins. This helps the RAI to be absorbed correctly.

Do your best to follow the LID but remember it is not possible or necessary to follow a diet that has no iodine. The aim is to avoid having high iodine levels. Most doctors agree that following the LID makes only a small difference to the effectiveness of your treatment.

This diet was developed by the UK Low Iodine Working Group 2016 and updated in 2023 by the UK Low Iodine Revision Working Group.

Where is iodine found?

Iodine is found in many foods in varying amounts. It is essential for good health. The foods with the highest iodine are those from the sea, dairy produce, and eggs. 

In many countries iodine is added to salt. This does not happen routinely in the UK, therefore it is fine to use UK table salt so long as it is not labelled as being iodised.

Some milk-alternative drinks such as oat drink, soya drink and almond drink are fortified with iodine (usually labelled as potassium iodide or potassium iodate) and/or contain carrageenan or lithothamnium (seaweed derivatives which are high in iodine). Always try to check the labels carefully for suitable products that do not contain these ingredients. It is not necessary to use organic dairy alternatives (such as an organic soya drink), but it may be helpful to know that these products cannot be fortified with iodine.

How long should the LID be followed for?

The diet is for a short time only. Evidence suggests that following it for just one week is sufficient and will ensure that your iodine levels are not high. Two hours after you have received the RAI treatment you can return to your normal diet.

What if I eat something high in iodine by mistake?

Eating a high iodine food accidentally is unlikely to affect your treatment. If you do, just carry on with the LID recommendations provided here.

Should I look on the internet for further information?

Much of the LID information which is found online is written for patients in countries where the food is produced using iodised salt or where other products like flour have iodine added. Guidance from the internet is often not relevant for people living in the UK and it can be confusing. 

Special diets

If you are currently following a diet under medical guidance (e.g. for diabetes or coeliac disease) please discuss this with your thyroid team and/or your dietitian.

If you have any questions about the LID please contact the medical professionals who are looking after you. 

LID Frequently Asked Questions 

LID meal suggestions