March 21, 2017


Other name(s):

iodide, organic iodine, potassium iodide, sodium iodide

General description

In 1922, experts learned that the thyroid gland needs iodine. The gland needs it to make thyroid hormones and prevent enlarged thyroid glands (goiter). Thyroid hormones control metabolism. They also affect reproductive processes, nerves, muscles, skin, and hair. Iodine also helps with the synthesis of protein and utilization of oxygen.

Iodine is in two main hormones made by the thyroid gland. Together, these hormones control the metabolic rate of the body. They’re important in growth and development, especially in the fetus and newborn. Not having enough iodine and thyroid hormones can cause intellectual issues and developmental delays.

Medically valid uses

Iodine is used to prevent and treat goiters and over-active thyroid gland (hyperthyroidism). It’s also used to prevent and treat iodine deficiency and thyrotoxic crisis.

Consuming table salt fortified with potassium iodide can help prevent goiters. Other sources of iodine include eggs, dairy products, and seaweed.

If you get goiter during pregnancy, you’ll need treatment. This can keep your baby healthy.  

Unsubstantiated claims

Please note that this section reports on claims that have not yet been substantiated through studies.

Iodine is said to reduce the risk of breast cancer, decrease fatigue, and stave off weight gain. It may also help treat hardening of the arteries (arteriosclerosis).

Recommended intake

People living in the Great Lakes states need iodine supplements. This area is even called the "goiter belt". People living in other areas without enough iodine in the soil also need supplements. Before iodine was added to table salt, it’s thought that 50–70% of people living in the Lake Michigan area had goiters.

Adults who don’t get enough iodine in their diet can get goiters. In severe cases, this may lead to an underactive thyroid gland (hypothyroidism). Symptoms can include:

  • Memory and cognitive issues

  • Decreased alertness

  • Dry skin and hair

  • Weight gain

People who consume large amounts of "goitrogenic" vegetables also need more iodine. These include cabbage, kale, Brussels sprouts, and rutabagas. These substances keep the digestive tract from absorbing iodine. Cooking deactivates goitrogenic substances.

Newborns that didn’t get enough iodine during pregnancy are often born with enlarged thyroids. They may also have signs of hypothyroidism. If a fetus’s thyroid doesn’t work during development, he or she can get cretinism. These problems can lead to intellectual issues. They can also cause growth problems.  

Iodine is measured in micrograms. The Recommended Dietary Allowance (RDA) is as follows:



Infants (0 to 6 months)

110 mcg*

Infants (7 months to 1 year)

130 mcg*

Children (1–3 years)

90 mcg

Children (4–8 years)

90 mcg

Children (9–13 years)

120 mcg

Males (14 years and older)

150 mcg

Females (14 years and older)

150 mcg

Pregnant women

220 mcg

Breastfeeding women

290 mcg

*Adequate Intake (AI)

Food source

Nutrient content per 100 grams


61,990 mcg*

Iodized salt

10,000 mcg

Cod liver oil

838 mcg

Seafood, fish (depending on type of fish)

36–311 mcg

Seafood, shellfish (depending on type of shellfish)

31–129 mcg

Sea salt

94 mcg

Side effects, toxicity, and interactions

Elemental iodine is poisonous. This type is found in "tincture of iodine". It’s used to disinfect cuts. Ingesting even a small amount can cause death.

Taking in too much iodine may cause a goiter. It may also keep your thyroid from working well. This is more likely if you take doses close to 1,000 mcg per day.

Women who are pregnant or breastfeeding shouldn’t take iodine supplements without talking to their healthcare providers. Too much iodine during pregnancy may cause hypothyroidism and a goiter in a newborn.

People who take lithium shouldn’t take iodine supplements. Using these two substances together can cause hypothyroidism. You also shouldn’t take iodine supplements if you’re taking amiodarone.

Additional information

Many areas of the country have very little iodine in the soil. As a result, crops in these areas and animals raised on these crops are exposed to little iodine. Before iodine was added to table salt, many people in these areas had goiters. This problem has mostly gone away now. This is likely due to iodized salt and the widespread consumption of ocean fish and shellfish.

Iodized salt contains potassium iodide. It’s often in a ratio of one part iodine to 10,000–100,000 parts salt. This means there’s very little iodine in the salt. But it’s enough to prevent goiter. Iodized salt made in the U.S. contains 76–100 mcg of iodine per gram of salt.


March 21, 2017


The Thyroid, Iodine and Breast Cancer. Smyth, PP. Breast Cancer Research. 2003, issue 5, pp. 235–238.

Reviewed By:  

Poulson, Brittany, RD, CDE,Wilkins, Joanna, R.D., C.D.