What to Know About Potassium Iodide for Nuclear Radiation Emergencies

Medically Reviewed by Neha Pathak, MD on March 18, 2022

Potassium iodide (KI) is a salt that can help protect you from radioactive iodine. Your thyroid gland is the part of your body that’s most sensitive to radioactive iodine. Potassium iodide can help block your thyroid from absorbing radioactive iodine if you are exposed to it.

But the salt doesn’t protect the rest of your body from radioactive iodine, only your thyroid. It also can’t reverse any health issues caused by radioactive iodine if your thyroid was already damaged.

The Food and Drug Administration (FDA) released guidance in December 2001 on how to safely use potassium iodide. In pill or liquid form, it can help protect you during a nuclear radiation emergency.

How Does Potassium Iodide Work?

If you’re in an area that’s had a radiation emergency, the most effective option is evacuation. But potassium iodide can act as an extra measure to keep you safe.

When you take potassium iodide, your thyroid gland absorbs it. If you get the right amount at the right time, it will saturate your thyroid gland. This can help block any inhaled or ingested radioactive iodine from being absorbed by your thyroid. This lowers your risk for radiation damage to that gland.

When Should You Take Potassium Iodide Pills?

Only take potassium iodide if state or local health authorities suggest you do so. During an emergency, health officials will send out an announcement. Your health department will then tell you when it’s OK to take potassium iodide. They’ll also tell you when you can stop the medication.

You’ll take potassium iodide before or right after you’re exposed to radioactive iodine. You could also take it 3 to 4 hours after, but it won’t be as effective.

It’s important to take the medication once a day until the risk of radiation exposure no longer exists. Don’t take larger amounts or extra doses unless experts recommend to. A larger amount of potassium iodide won’t protect you more from radioactive iodine. Too much of the medication could put you at a higher risk for side effects.

Guidance is slightly different for everyone:

Infants and young children. Newborns and children are most at risk for a thyroid injury from radioactive iodine. Those with low amount of iodine in their thyroid are also likely to have thyroid damage.

Because of this, it’s important to give children, especially newborns, potassium iodide during an emergency.

People who are pregnant or breastfeeding. It’s also crucial that pregnant and breastfeeding individuals take the proper dose of potassium iodide to protect themselves and their baby.

Young adults. This group is less sensitive to the potential damage from radioactive iodine. But it’s still important for them to take the medication.

Adults. People over the age of 40 should only take potassium iodide if their public health officials state that there will be a very high amount of radioactive iodine contamination. This group has the lowest risk of thyroid cancer or thyroid injury after radioactive iodine exposure. They’re also at the highest risk of an allergic reaction or adverse effects from potassium iodide.

How Much Potassium Iodide Should You Take?

You should take a different amount of potassium iodide based on your age and weight. There’s a liquid form, a 65-milligram pill, and a 130-milligram pill. For kids and babies that can’t take pills, you can crush or cut pills to create smaller doses. Or you can give them a liquid form of potassium iodide.

Follow these dosing guidelines:

Adults 18 years old and up:

  • Take one 130-milligram pill of potassium iodide, or
  • 2 milliliters of liquid potassium iodide, or
  • 2 tablets of 65-milligram potassium iodide

Children 12 to 18 years old who are over 150 pounds:

  • Take one 130-milligram pill of potassium iodide, or
  • 2 milliliters of liquid potassium iodide, or
  • 2 tablets of 65-milligram potassium iodide

Children 12 to 18 years old and less than 150 pounds:

  • Take one 65-milligram pill of potassium iodide, or
  • 1 milliliter of liquid potassium iodide, or
  • Half of a 130-milligram potassium iodide tablet

Children 3 to 12 years old:

  • Take one 65-milligram pill of potassium iodide, or
  • 1 milliliter of liquid potassium iodide, or
  • Half of a 130-milligram potassium iodide tablet

Children 1 month to 3 years old:

  • Take half of a 65-milligram potassium iodide tablet, or
  • 0.5 milliliters of liquid potassium iodide, or
  • A fourth of a 130-milligram potassium iodide tablet

Newborns to children 1 month old:

  • Take a fourth of a 65-milligram potassium iodide tablet, or
  • 0.25 milliliters of liquid potassium iodide, or
  • An eighth of a 130-milligram potassium iodide tablet

It can be hard to cut pills. In an emergency, experts say that it’s safe for children at school or day care centers to take a whole pill of potassium iodide. If possible, it’s better that kids under 12 take the 65-milligram pill. But it’s still safe to have them take the 130-milligram pill if it’s the only one available.

Are There Any Side Effects From Potassium Iodide?

In general, most people can take potassium iodide without any problems. But it’s always important to talk to your doctor before you use it. If you have certain medical conditions, it might not be a good idea to take the medication.

Carefully watch babies to ensure their safety if they take potassium iodide.

You might notice some side effects after you take potassium iodide. They can include:

  • An upset stomach
  • Allergic reactions
  • Rashes
  • Inflammation in your salivary glands

Thyroid gland complications could also happen. But this is rare. They’re more likely if you:

  • Take a higher dose of potassium iodide than what’s recommended
  • Take the medication for many days
  • Have pre-existing thyroid disease

A newborn (a baby less than 1 month old) could develop hypothyroidism if they take more than the suggested amount of potassium iodide. Hypothyroidism is a condition where your thyroid hormone levels are too low. If doctors don’t treat this, it can cause brain damage. To keep your infant safe:

  • Get your child’s hormone levels checked if they received more than a single dose of potassium iodide. Your doctor should continue to monitor their levels.
  • Stay away from repeat dosing of potassium iodide for infants.

Where Can You Get Potassium Iodide?

You don’t need a prescription to get potassium iodide. You can get it over the counter at local pharmacies or drugstores. If it’s not available near you, you can order potassium iodide online. Make sure that the FDA has approved the version that you get.

Store your potassium iodide in a dark, dry, and cool place. In this setting, it can last for about 5 to 7 years.

Show Sources


CDC: “Potassium Iodide (KI).”

FDA: “Frequently Asked Questions on Potassium Iodide (KI),” “Guidance Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies.”

New York State Department of Health: “Potassium Iodide (KI) and Radiation Emergencies: Fact Sheet.”

United States Nuclear Regulatory Commission: “Frequently Asked Questions About Potassium Iodide.”

Mayo Clinic: “Potassium Iodide (Oral Route).”

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