Potassium Iodide (KI)

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What is potassium iodide?

Potassium iodide is a chemical compound that contains iodine, which is necessary for the normal functioning of the thyroid gland. It is known by its chemical symbol, KI.

Potassium iodide is the iodine in iodized salt. Most people ingest it every day without being aware of it.

Potassium iodide is also manufactured in pill form to be used as a supplement to help prevent the thyroid gland from absorbing radioactive iodine that might be released during an emergency at a nuclear power plant. It is intended to protect against thyroid gland cancer caused by radioactive iodine.

Potassium iodide is not an “anti-radiation” pill. It is only effective at protecting the thyroid from radioactive iodine-131.

How does it work?

Potassium iodide protects the thyroid gland by preventing the accumulation of radioactive iodine. When taken under the direction of public health officials, potassium iodide is absorbed into the thyroid gland, thus protecting it from absorbing any radioactive iodide. Potassium iodide does not protect parts of the body other than the thyroid gland, nor does it provide protection against other forms of radiation.

What are the side effects of potassium iodide?

Side effects are unlikely because of the low dose and the short time you will take the drug. Possible side effects include skin rashes, swelling of the salivary glands, and “iodism” (metallic taste, burning mouth and throat, sore teeth and gums, symptoms of a head cold and sometimes stomach upset and diarrhea).

A few people may have an allergic reaction with more serious symptoms. Those could be fever and joint pain, or swelling of parts of the face and body and at times severe shortness of breath requiring immediate medical attention.

In rare instances taking potassium iodide may cause over activity, under activity, or enlargement of the thyroid gland (goiter).

What should I do if side effects occur?

If side effects are severe or if you have an allergic reaction, stop taking potassium iodide. Then, call a doctor or public health authority for instructions.

Is taking potassium iodide mandatory?

No. The use of potassium iodide is voluntary. No one is required to accept or use it.

Where can I get potassium iodide?

In 2001 Potassium Iodide (KI) was implemented as a protective measure due to health risks to the public and emergency responders from Iodine-131 released from an active and operating nuclear reactor. Potassium iodide is used to protect the thyroid gland from a specific type of radioactive iodine (iodine-131), which could be released to the environment in a nuclear power plant accident. Iodine-131 is produced during the fission process at an operational nuclear power plant, and naturally decays to undetectable levels in less than 80 days.

Due to the fact that SONGS has been shut down for over two years and is in the process of permanent decommissioning, and because there is no longer a risk of an I-131 release with no fission occurring, Orange County Health Officer, Dr. Eric Handler agrees with statements issued from the Nuclear Regulatory Commission (NRC) and the Federal Emergency Management Agency (FEMA) that KI is no longer a necessary protective measure. Because of this, the City of San Clemente is suspending the KI distribution program. 

If you would like to purchase potassium iodide, it can be purchased without a prescription. The following manufacturers are approved for the sale and distribution of potassium iodide by the U.S. Food and Drug Administration:

Phone: 1-866-463-6754 (toll free)
Brand name: IOSAT™ tablets
Phone: 1-866-849-7672 (toll free)
Brand name: ThyroSafe™ tablets

For more information about Potassium Iodide, including the age range in which it is most effective, please visit theU.S. Food and Drug Association’s KI Question and Answer Page.

KI Fact Sheet Printable Version (PDF).

KI Fact Sheet (Spanish Language) (PDF).

For more information contact:
Stephen Foster, Emergency Planning Coordinator, (949) 361-6109

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