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Overview: Potassium iodide is used to prevent radiation damage to the thyroid during a radiation emergency. It is also used to help break up mucus in people with certain long-term lung conditions. Common side effects include diarrhea, nausea, vomiting, rash, swollen salivary glands, and stomach pain. Serious side effects are rare but can include thyroid problems or iodine poisoning. Potassium iodide is available as a prescription medicine and over the counter. Before taking potassium iodide, tell your health care provider about all of your health conditions and any medicines or supplements you may be using.

Uses

What is potassium iodide used for?

Potassium iodide is used to help prevent radiation damage to the thyroid during a nuclear radiation emergency.

Potassium iodide is also used to help break up mucus in people with certain lung conditions, such as asthma or chronic obstructive pulmonary disease (COPD).

Potassium iodide may also be used for other conditions as determined by your health care provider.

Note: The Food and Drug Administration (FDA) has not reviewed some forms of potassium iodide for safety and effectiveness, and some product labels are not approved by the FDA. Learn more about unapproved drugs here.

Potassium iodide is a form of iodine. See Iodine[1]  for more information on other products that contain iodine.

How does potassium iodide work (mechanism of action)?

Potassium iodide contains iodine, which is a mineral that your thyroid uses to make thyroid hormones.

During a radiation emergency, you could be exposed to radioactive iodine. Your thyroid can absorb radioactive iodine, increasing your risk for thyroid cancer and other serious conditions in the future. Taking potassium iodide during a radiation emergency can help protect your thyroid from radioactive iodine. If you take potassium iodide 24 hours before exposure to radiation or four hours after exposure, your thyroid will absorb the iodine in potassium iodide instead. 

Potassium iodide can also work as a mucolytic, which means that it can help break up mucus in the lungs. If you have a long-term lung condition that causes thick mucus, such as asthma or COPD, this can help make it easier to breathe.

How is potassium iodide supplied (dosage forms)?

Brands and other names

  • iOSAT
  • SSKI 
  • ThyroSafe

Example dosage forms and strengths

  • 65 mg/mL, 1 g/mL oral solution
  • 65 mg, 130 mg oral tablets

How should I store potassium iodide?

Potassium iodide should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place, and protect from light. Keep the container tightly closed.

 

Side Effects

What are the most common side effects of potassium iodide?

The most common side effects of potassium iodide are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

  • Diarrhea
  • Nausea or vomiting
  • Rash
  • Swollen or tender salivary glands
  • Stomach pain or discomfort

There may be other side effects of potassium iodide that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of potassium iodide?

While less common, the most serious side effects of potassium iodide are described below, along with what to do if they happen.

Severe Allergic Reactions. Potassium iodide may cause allergic reactions, which can be serious. Stop taking potassium iodide and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart or chest pain
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Swelling of the hands or feet
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives, which can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Thyroid Problems. Potassium iodide can cause the function of your thyroid gland to change. This can raise thyroid hormone levels (hyperthyroidism), lower thyroid hormone levels (hypothyroidism), or cause your thyroid to grow larger (thyroid goiter). Keep all appointments to have your blood checked. Tell your health care provider if you have any of the following signs of thyroid problems.

  • Weight gain or weight loss
  • Feeling unusually cold or hot
  • Tiredness that does not go away or continues to worsen
  • Mood swings
  • Trouble sleeping
  • Constipation
  • Tightness in your throat
  • A hoarse voice

Iodine Poisoning. People who regularly take large amounts of potassium iodide may have iodine poisoning. This is sometimes called iodism. To reduce the risk of iodine poisoning, follow your health care provider’s instructions or the instructions on the package. Do not take potassium iodide for longer than recommended. Keep all appointments, including those for lab tests, while you are taking it. Stop taking potassium iodide and call your health care provider right away if you have any of the following symptoms of iodine poisoning.

  • Sore gums or teeth
  • Bad headaches
  • The whites of your eyes seem red
  • Swollen eyelids
  • Blurry vision
  • Your eyes water, your nose runs, or you have more spit in your mouth than usual

Warnings & Precautions

Who should not use potassium iodide?

Allergies to Ingredients. People who are allergic to any of the following should not take potassium iodide.

  • Iodine
  • Iodine/potassium iodide (Lugol’s solution)
  • iOSAT
  • Potassium iodide
  • SSKI 
  • ThyroSafe
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific potassium iodide products they stock.

A Skin Condition Called Dermatitis Herpetiformis. Taking potassium iodide may make this condition worse. Let your health care provider know if you have dermatitis herpetiformis before taking potassium iodide.

A Rare Condition Called Hypocomplementemic Vasculitis (HUVS). Taking potassium iodide may make this condition worse. Let your health care provider know if you have HUVS before taking potassium iodide.

What should I know about potassium iodide before using it?

There are multiple forms of potassium iodide available. If potassium iodide was prescribed to you by a health care provider, take it as prescribed. If you are using over-the-counter potassium iodide, follow the instructions that come with the product. If you have any questions about how to take potassium iodide, talk to your health care provider.

Do not share potassium iodide that was prescribed for you by a health care provider with other people, even if they have the same condition as you. It may harm them.

Keep potassium iodide out of the reach of children.

Taking potassium iodide with food or milk may help reduce stomach discomfort.

If you are taking liquid potassium iodide, it must be mixed into another liquid before use, such as water, juice, or milk. Use an accurate measuring device to measure your dose. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist what measuring device to use. 

At cold temperatures, crystals may form in liquid potassium iodide. These crystals can dissolve back into the liquid once it is warmed up and gently shaken. But if your potassium iodide turns brownish-yellow, it should be thrown away and replaced. Ask your health care provider if you have any questions.

If you are taking potassium iodide tablets, take them as directed. If you or your child is not able to swallow the tablet whole, the tablets may be crushed and mixed with milk, formula, water, orange juice, flat soda, or raspberry syrup. Take the dose soon after it is mixed. 

If you are planning to take potassium iodide for a radiation emergency, it is important to know that potassium iodide can only protect you from radioactive iodine. This is only one of many forms of radiation that can cause harm during a radiation emergency. Learn about other important ways to protect yourself and your family from radiation here.

Infants who are under 1 month old are at greater risk of side effects from potassium iodide. They are also at greater risk of harm from radioactive iodine. Talk to your health care provider about how much potassium iodide your child should take during a radiation emergency. 

People who are 40 years or older may be at greater risk of side effects from potassium iodide but are at lower risk of harm from radioactive iodine. If you are in this age group, you may only need to take potassium iodide during certain types of radiation emergencies. Talk to your health care provider about your options.

What should I tell my health care provider before using potassium iodide?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if potassium iodide is right for you.

In particular, make sure that you discuss any of the following.

Thyroid Problems. Taking potassium iodide regularly may make certain thyroid problems worse. Tell your health care provider if you have any thyroid problems, such as high or low thyroid hormone levels, thyroid nodules, a thyroid goiter, autoimmune thyroiditis, or Graves’ disease.

Other Current and Past Health Conditions. Tell your health care provider if you have any of the following.

Other Medicines and Supplements. Potassium iodide may interact with other medicines and supplements. Before taking potassium iodide, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Potassium iodide may cause harm to a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. If you are taking potassium iodide during a radiation emergency, your health care provider will let you know if you should take more than one dose of potassium iodide while you are pregnant or trying to get pregnant.

Breastfeeding. Potassium iodide passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should stop breastfeeding or stop potassium iodide. Learn more about breastfeeding during a radiation emergency here. 

Interactions

Does potassium iodide interact with foods or drinks?

There are no known interactions between potassium iodide and foods or drinks. Taking potassium iodide with food or milk may help reduce stomach discomfort.

It is unknown if drinking alcohol will affect potassium iodide.

Does potassium iodide interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking potassium iodide.

  • Amiloride (Midamor), eplerenone (Inspra), spironolactone (Aldactone, Carospir), or triamterene (Dyrenium), which are diuretics, also called water pills
  • A thyroid medicine, such as levothyroxine, which is used to raise thyroid hormone levels 
  • An angiotensin-converting enzyme (ACE) inhibitor, such as enalapril or lisinopril, which is a medicine for high blood pressure, heart failure, and certain kidney problems
  • An angiotensin II receptor blocker (ARB), such as losartan or valsartan, which is a medicine for high blood pressure, heart failure, and other heart conditions
  • An antithyroid medicine, such as methimazole or propylthiouracil (PTU), which is used to lower thyroid hormone levels
  • An iodine supplement
  • Lithium, which is a medicine for certain mental health conditions

This may not be a complete list of medicines that can interact with potassium iodide. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much potassium iodide?

If you or someone else has used too much potassium iodide, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of potassium iodide?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.