Potassium Iodide

Potassium Iodide (KI) - FAQ


potassium iodide molecule - KIWhat is potassium iodide?

Potassium iodide, also known by its chemical symbol KI, is a substance similar to table salt. ("Iodized" salt, is salt with potassium iodide added.) In medicine, it is used to treat certain thyroid and lung problems, iodine deficiencies, and some skin fungi. However, it is best known as a drug which can protect your thyroid in the event you are exposed to radioactive iodine - for example, as the result of an accident at a nuclear power plant.

Does it protect against all types of radiation?

No. Potassium iodide (KI) only protects one part of your body (your thyroid gland) against radioactive iodine - also known as radioiodine or iodine-131. Radioiodine is an "unstable" form of iodine, which can cause thyroid cancer. Thyroid cancer from exposure to radioactive iodine is a very common and serious health problem associated with nuclear accidents.

How does potassium iodide protect you from radioactive iodine?

Taking potassium iodide "blocks" the uptake of radioactive iodine by your thyroid by filling it with "good" iodine. This prevents your thyroid from absorbing any radioactive iodine for the next 24 hours.

Who is the most at risk from radioiodine (radioactive iodine)?

Infants, children and unborn babies are at the highest risk of developing thyroid cancer from radioiodine exposure.

Do I need a prescription to buy potassium iodide (KI)?

No - Potassium Iodide is classified as a supplement, not a drug, and is available for purchase over-the-counter or online. Look for brands which have been approved by the FDA, like IoSAT or ThyroShield.

potassium iodide pillsHow is it sold?

Potassium Iodide is available in pills or liquid. Pills are sold in strengths of either 65mg or 130mg, liquid is 65mg per milliliter. Pills are scored so they can be cut in half if necessary.

Where can I buy Potassium Iodide?

You can buy it over-the-counter or online from sites like Nukepills.com. A major supplier of FDA-approved Potassium Iodide, Nukepills donated donated 54,000 doses of KI to the people of Japan following the Fukushima disaster. Nukepills stocks both the IoSAT and ThyroShield brands, including the hard-to-find ThyroShield liquid for children.

Visit Nukepills.com

How long can I store it?

The pills normally have a shelf life of 5-7 years, the liquid has a shelf life of 5 years. KI should be stored in a cool, dark place or according to the manufacturer's recommendations.

When should it be taken?

Potassium iodide should be taken when directed by public health officials, either just prior to or immediately after an anticipated exposure to radiation. It can still be effective if taken up to 3-4 hours after exposure. It should only be taken when you are at risk of exposure, and until you are evacuated to safety.

Should I give potassium iodide to my children?

Yes. Since babies and children are at the highest risk of developing thyroid cancer, the CDC and FDA advise that infants, children and pregnant women should be given potassium iodide if they will be exposed to radioactive iodine unless it is contraindicated by other medical conditions (allergies, etc.)

How much Potassium Iodide should I take? How much should I give to my children?

Age Group Anticipated
Exposure (cGy)
Iodide - Dose
(65 mg/mL)
# of 65-mg tablets # of 130-mg tablets
Adults over 40 years Over 500 130 mg 2 mL 2 1
Adults 18-40 years 10 or more 130 mg 2 mL 2 1
Women who are pregnant or nursing 5 or more 130 mg 2 mL 2 1
Over 12 - 18 years and over 150 pounds 5 or more 130 mg 2 mL 2 1
Over 12 - 18 years and less than 150 pounds 5 or more 65 mg 1 mL 1 1/2
Over 3 - 12 years 5 or more 65 mg 1 mL 1 1/2
Over 1 month to 3 years 5 or more 32 mg 0.5 mL 1/2 1/4
Birth - 1 month 5 or more 16 mg 0.25 mL 1/4 1/8

Source: US Food and Drug Administration

*   Potassium iodide oral solution comes in 1 oz (30 mL) bottles with a dropper marked for 1, 0.5, and 0.25 mL dosing.  each mL contains 65 mg potassium iodide. If you have babies or infants, the liquid is highly recommended.

** Babies or children who can't swallow pills can be given the liquid. Or, the pill can be crushed and mixed with liquid, such as water and a little juice to make it more palatable - See Home Preparation Procedure for Emergency Administration of Potassium Iodide Tablets to Infants and Small Children for instructions. ThyroShield™makes a flavored liquid for children and infants. 

How long should it be taken?

Babies and pregnant or breastfeeding women should only take ONE dose unless directed otherwise by a health professional. Giving additional doses to infants, especially newborn babies, can interfere with normal development. In an emergency, these individuals should be given priority with respect to evacuation and sheltering.

For everyone else, potassium iodide can be taken once every 24 hours, until health officials tell you to stop, and/or until you are out of the emergency zone.

What happens if I take a dose when I didn't need to?

Generally nothing - it should be out of your body in 24-48 hours.

However, this is NOT something to take routinely or long term. Take potassium iodide only in an emergency and until the immediate danger has passed.

Are there side-effects from potassium iodide (KI)?

People sometimes experience:

More severe side effects, often associated with an iodine allergy, include:

If you experience severe symptoms, seek prompt medical attention.

Adverse reactions are more likely to occur from taking higher dosages, long-term usage or in adults over age 40.

Long-term usage can cause an under-active or overactive thyroid or goiter (an enlarged thyroid gland.)

Are there people who should NOT take potassium iodide?

Yes! KI (potassium iodide) should NOT be taken by:


What should I do if I experience side effects?

Consult with a health professional. If side effects are severe, stop taking KI and seek immediate medical assistance.


The Centers for Disease Control - http://www.bt.cdc.gov/radiation/ki.asp
US Food and Drug Administration - http://www.fda.gov/drugs/emergencypreparedness/bioterrorismanddrugpreparedness/ucm072265.htm
Nuclear Regulatory Committee - http://www.nrc.gov/about-nrc/emerg-preparedness/about-emerg-preparedness/potassium-iodide/ki-faq.html#10mile
The World Health Organization - http://www.who.int/ionizing_radiation/pub_meet/Iodine_Prophylaxis_guide.pdf

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