Toxicity of Iodine

Iodine is a trace mineral that is naturally found in the human body and is also derived from food sources such as dairy products, kelp, haddock, cod, perch and sea bass. In the United States, table salt is typically fortified with iodine. Multivitamins and potassium iodide supplements also serve as sources of this mineral. In rare cases, overconsumption of iodine can lead to toxicity.

A plate of seaweed salad on a bamboo mat.
Credit: Amawasri/iStock/Getty Images

Tolerable Upper Limit

The recommended daily intake of iodine for adults is 150 micrograms, according to the Linus Pauling Institute at Oregon State University. However, the tolerable upper limit, which represents the maximum safe dosage, is 1,100 micrograms for adults. Most people, except for those in areas such as Northern Japan known for heavy seaweed consumption, consume less than 1,000 micrograms of iodine per day.

Moderate Toxicity

Moderate toxicity is typically marked by elevated levels of thyroid stimulating hormone, or TSH, in the bloodstream. Moderate toxicity, which can occur at levels above the tolerable upper limit, may result in hypothyroidism, or insufficient production of thyroid hormones that regulate metabolism of food nutrients. Consumption of more than 1,700 micrograms of iodine per day may cause goiter, or enlargement of the thyroid gland, according to the Linus Pauling Institute.

Acute Toxicity

Acute toxicity typically occurs at dosages of more than 1 gram of iodine, according to the Linus Pauling Institute. Acute iodine toxicity may cause symptoms such as diarrhea, nausea and vomiting, as well as a burning sensation in the stomach, throat and mouth. Weak pulse and coma are also potential complications of acute toxicity.


Although heavy consumption of iodine may cause toxic symptoms, this mineral serves important functions in the human body when taken in recommended doses. Iodine aids in the metabolism of nutrients for energy, according to the University of Maryland Medical Center. It also supports proper thyroid function and may help prevent cretinism, a type of mental and physical retardation.

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