Potassium Iodide and the Distribution Program

Read the PDF version

What is KI?

Potassium iodide is a salt that contains iodine. Its chemical symbol is KI. It is a medicine that is available for over-the-counter sale.

KI has been determined by the U.S. Food and Drug Administration (FDA) to be a safe and effective method to block exposure to radioactive iodine—radioactive iodine is one specific product of a nuclear release. Radioactive iodine, if inhaled or ingested through contaminated food or milk, can increase the risk of developing thyroid cancer.

In case of an overdose or allergic reaction – call your physician or the New England Poison Center at 800-222-1222.

How does KI protect against cancer?

Certain types of iodine help your thyroid function properly. Most people get the iodine they need from foods like fish and iodized salt. The thyroid absorbs and stores iodine, but it can hold only so much at one time. Because of this, one dose of KI, which is not harmful to the thyroid, fills the thyroid so it cannot take up any radioactive iodine that may be released in a nuclear emergency.
For best protection, one dose of KI should be taken just before or at the time of exposure, although it may still lower the risk of thyroid cancer even if taken three or four hours following exposure.
Treatment guidance from the FDA confirms that the benefits of KI far outweigh the rare risks of serious side effects. This is especially true for children, who are more likely than adults to develop thyroid cancer following exposure to radioactive iodine. FDA’s guidance is based on a review of studies conducted after the 1986 Chernobyl nuclear reactor accident.

IMPORTANT The protection offered by KI is very specific. It protects one organ (thyroid gland) from one type of radiation exposure (radioactive iodine). Emergency directives such as evacuation, staying indoors, or restricting the use of contaminated food and milk are designed to minimize your exposure to all types of harmful radiation that could be released in a nuclear emergency. Taking KI is not a substitute for following emergency directives.

Who should NOT take KI?

If you are not sure if you should take KI, talk with your healthcare provider.

What is the correct dose?

See also: Special instructions for administering potassium iodide to children

The US Department of Health and Human Services and the Nuclear Regulatory Commission have supplied Vermont with 65 milligram (mg) size tablets, which are marked so they can easily be cut in half. KI should not be given to children unless directed to do so by public health officials in the event of a radiological emergency at Vermont Yankee, and then only at FDA recommended dosages.


FDA recommended dose

# of 65 mg

Adults over 18 years

130 mg


Pregnant or breastfeeding women

130 mg


Children over 3 years to 18 years*

65 mg


Children 1 month to 3 years

32 mg


Children under 1 month

16 mg


*Children who weigh 154 pounds or more should receive the adult dose.

Special instructions for administering KI to children

For children over age 3 years to 18 years– for children weighing less than 154 pounds – the correct dose is one 65 mg tablet of KI.
For children in this age group who may not be able to swallow a tablet, powder may be a better choice.

To make the powder:

For children 1 month to 3 years – the correct dose for this age group is 32 mg of KI.

For children in this age group, the correct dose is one-half (1/2) of the 65 mg tablet. Follow the instructions above if the child needs to have the portion of the pill crushed into a fine powder. 

For infants up to 1 month old – the correct dose is 16 mg of KI.

For newborns, the dose is one-quarter (1/4) of a 65 mg tablet.

How can I dispose of expired KI?

If you have expired KI it can be disposed of like prescription medicines:


Schools and licensed childcare facilities within the six towns of the Emergency Planning Zone next to Vermont Yankee are prepared to dispense KI to children in a radiological emergency, if there is written consent from a parent or guardian. Schools and childcare facilities work with state officials regarding KI emergency procedures.

In case of an overdose or allergic reaction – call your physician or the New England Poison Center at 800-222-1222.

KI is effective if taken shortly before (about 30 minutes) or after (up to 3 hours) exposure to radioactive iodine in the air. Vermont Department of Health officials will work to anticipate possible radiological releases from Vermont Yankee and issue orders for KI administration to fit into this time frame.

Return to Top