Potassium Iodide – Radiation Protection

This is not medical advice – always talk to your doctor before taking any form of medication

What Are Potassium Iodide Tablets?

Potassium Iodide (KI) tablets are a medication that is taken during nuclear emergencies to protect your thyroid gland from absorbing radioactive iodine isotopes. In nuclear bombs and reactors, the uranium isotopes decay into radioactive iodine isotopes. Your body can’t tell the difference between the radioactive isotopes of iodine and the safe ones. If you ingest or inhale the radioactive isotopes, your body will absorb them and they congregate in the thyroid. These pills give your body enough iodine to stop it absorbing the radioactive isotopes and so they pass straight through you.

During the Chernobyl and Fukushima incidents Iodide-131 (131I) was deemed the most important with respect to the public’s exposure [1]. 131I will also be the dominant radioisotope in solution (i.e. in bodies of water) for the first few months after a disaster [2] meaning there is a high risk of ingestion. Children are particularly at risk of absorbing 131I.

When And How To Take KI

KI should only be taken when you are instructed to by public health or emergency response officials or a doctor. It is most effective when taken shortly before exposure to radiation. They should be taken 24 hours before exposure to be most effective and can be taken up to 4 hours after and still retain some effectiveness [3]. You should check if you are safe to take potassium iodide with a doctor before an emergency happens.

One dose of potassium iodide will protect you for 24 hours [4] and the doses for different ages can be found to the right.

Potassium Iodide dosage by age
** The U.S.FDA provides instructions on how to make oral potassium iodide solution at home using KI tablets.
***Adults over 40 should only take KI when recommended by officials when predicted exposure levels are high enough to possibly cause hypothyroidism.

Source: Centres for Disease Control and Prevention

Is Potassium Iodide Safe To Take?

Some people can have adverse reactions to potassium iodide or iodine allergies. You should check with your doctor before taking any medication. Adults over the age of 40 are more likely to suffer adverse effects from KI and children under one month may suffer from problems with normal development later if they take more than the recommended dose (although they are also at the highest risk of thyroid cancer from radioiodine). KI can cause other minor reactions such as gastrointestinal upset, rashes and inflammation of the intestinal gland [4].

The Radiation Safety Institute of Canada states that “In Poland, after the Chernobyl incident, single-dose stable iodine pills were given to 10 million children and no serious side effects were seen. Some minor side effects were noted including gastrointestinal upset and minor rashes. 7 million doses were given to adults at the same time, with only two severe adverse reactions, both in persons with a previously-known iodine allergy.” [5]

Do not try and use iodised table salt as a substitute for potassium iodide pills. Ingesting large amounts of salt an be harmful.

Limitations of KI

  • KI only protects against radiation from ingested radioiodine, it does not protect against other forms of radiation
  • KI only protects your thyroid, it does not protect an other parts of the body
  • KI is not an anti-radiation drug, you should still shelter in place in emergencies
  • KI does not offer 100% protection, your body will still absorb some radioiodine
  • KI cannot reverse damage already done to the thyroid

If you have enjoyed reading this article and want to learn how you can incorporate potassium iodide into a nuclear survival kit then check out this blog post. Otherwise have a look at our most recent posts below:


[1] K. V. Kotenko et Al, ‘Comparative analysis of the radionuclide composition in fallout after the Chernobyl and the Fukushima accidents’, 2012

[2] C. S. Shapiro et Al, ‘The Medical Implications of Nuclear War’, 1986

[3] New York State Department of Health, ‘Potassium Iodide and Radiation Emergencies: Fact Sheet’, accessed 30/01/2023

[4] Centres for Disease Control and Prevention, ‘Potassium Iodide (KI)’, accessed 30/01/2023

[5] Radiation Safety Institute of Canada, ‘Potassium Iodide Pills for Schools’, accessed 30/01/2023

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