What is Potassium Iodide? - Uses, Side Effects & Formula

Instructor: Kelsey Skodje

Kelsey has taught college chemistry and biochemistry and has a Ph.D. in bioinorganic chemistry.

This lesson will describe medical uses of potassium iodide, including its use as protection against radiation poisoning. You'll also learn about its side effects, chemical formula and structure, then you can test your knowledge with a short quiz.

What is Potassium Iodide?

Potassium iodide (KI) is a white, odorless solid that is typically used in its powder form, as shown in the image below. It's added to table salt as an important source of dietary iodine, and it can be ingested to protect the thyroid gland from nuclear radiation. Potassium iodide is nontoxic, unless used excessively, but can cause problems for people with iodine sensitivities.

Potassium iodide powder
KI Powder from wikimedia commons user Walkerma

Uses of Potassium Iodide

There are many ways in which potassium iodine can be used to promote good health. Below, we will review some of the more common uses for this important compound:

Iodized salt as protection from iodine deficiency disorders

Iodine is necessary for proper thyroid function, which is an important part of metabolism. Without enough iodine, thyroid enlargement occurs--this enlarged thyroid is called a 'goiter'. Even more importantly, an iodine deficiency inhibits fetal brain development, which can result in a reduction of 10-15 IQ points over a lifetime. In fact, iodine deficiency is one of the greatest causes of mental retardation.

Woman with an enlarged thyroid gland (goiter) due to iodine deficiency.

Seafood is an abundant natural source of iodine, but seafood isn't widely available in many parts of the world. Due to this, potassium iodide is added to table salt to make what's known as iodized salt. Iodized salt typically contains 0.006% to 0.010% potassium iodide. In the United States, about 70% of table salt is iodized, but iodine deficiency is still a serious health concern around the world.

Potassium iodide as protection from radiation poisoning

Potassium iodide is used to protect people from damage to the thyroid gland caused by radioactive iodine. Radioactive iodine is a byproduct of nuclear fission, and exposure can occur in the presence of nuclear reactors or weapons. If KI is taken within 3-4 hours after exposure, the stable iodine will 'fill' your thyroid, preventing radioactive iodine from entering and causing either acute damage or thyroid cancer.

An example of potassium iodide's use was in 1986 when the Polish government made it available to survivors of the Chernobyl nuclear reactor disaster. And in 2011, KI was provided after the Fukushima Daiichi nuclear disaster in Japan.

It's important to note that KI can only offer protection--it can't undo damage that has already occurred. In addition, its preventative effects only apply to thyroid damage from radioactive iodine. It has no effect on other types of radiation poisoning.

Potassium iodide as an expectorant

Potassium iodide is sometimes used to treat pulmonary diseases that cause a build-up of mucus in the lungs. Potassium iodide works as an expectorant, which means that it loosens this mucus, allowing it to be coughed up more easily.

Side Effects of Potassium Iodide

While potassium iodide is generally safe, it can cause some side effects, particularly if taken in excessive doses or for extended periods of time. These side effects can include allergic reactions, inflammation of salivary glands, and gastrointestinal upset. Another side effect is something called 'iodism', which consists of irritation of the mouth (including a metallic taste, a burning sensation, and sore teeth and gums) as well as symptoms of a head cold. Occasionally, iodism will come with an upset stomach and diarrhea.

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