March 28, 2011: What should you tell patients regarding purchase or ingestion of potassium iodide?

With the recent natural disaster in Japan and the resultant damage to the nuclear reactors in Fukushima Daiichi plant, there have been increased concerns about potential radiation exposure in the United States. As a result, there has been increased demand for potassium iodide (KI). KI is used to protect the thyroid from radioactive iodine.  The thyroid gland concentrates iodine as it is incorporated into thyroid hormones. Because the thyroid gland can rapidly absorb iodine, including radioactive forms, the thyroid is at risk when there is an exposure to radioactive iodine.  Exposure to radioactive iodine can result in long term hypothyroidism, similar to what occurs when patients are given I131 for treatment of hyperthyroidism.


KI is a non-radioactive potassium salt form of iodine. Ingestion of non-radioactive KI prior to exposure to radioactive iodine results in the thyroid gland being “flooded” with the stable form of iodine so the radioactive form is not taken up by the thyroid for the next 24 hours or so. KI does not protect the thyroid if taken after exposure and does not protect other body organs from effects of the radiation. KI also does not protect the body from other forms of radiation.


Currently, there is no expectation that the radiation from the Japanese nuclear power plants will result in harmful exposures in the United States. There is currently no public health concern in the US that would warrant administration of KI. However, some patients are seeking to stockpile or start taking KI. There are three FDA approved formulations of KI. Unfortunately, there are also many websites promoting their unapproved products which could be described as dietary supplements, iodine remedies, sea kelp therapies, etc.  If one your patients reports an adverse reaction from either an approved or unapproved product, please advise the FDA through their FDA MedWatch Adverse Event Reporting program: or calling 800-332-1088.


This question prepared by:  Saralyn Williams, MD  Medical Toxicologist


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Donna Seger, MD

Medical Director

Tennessee Poison Center


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