Iodine-induced hyperthyroidism isn’t common, but it is possible. Iodine can also be used to treat hyperthyroidism.

Woman eating a prawn.Share on Pinterest
anouchka/Getty Images

Iodine plays a key role in thyroid health. Iodine helps your thyroid gland make hormones that regulate your metabolism. When you get too little or too much iodine, it can prevent your thyroid from working properly.

Hyperthyroidism, also called an overactive thyroid, happens when your thyroid gland produces too many hormones. While the most common cause of this condition is Graves’ disease, an autoimmune disorder, consuming too much iodine can also cause it.

Iodine is a mineral naturally found in:

  • fish
  • seaweed
  • shrimp
  • dairy products
  • eggs

But iodized salt, which is salt with iodine added in, is one of the most common sources of iodine in the United States.

Because most people in the United States consume plenty of salt, iodine deficiency isn’t as common here as in other parts of the world.

Consuming too much iodine can affect your thyroid’s ability to function normally. It may lead to hyperthyroidism or hypothyroidism, which is an underactive thyroid.

While most healthy people can consume excess iodine without problems, some people have a higher risk of thyroid problems. In these people, even a single exposure to excess iodine levels can be consequential.

People most at risk of problems from excess iodine have experienced iodine deficiency in the past. Other risk factors include:

  • Graves’ disease
  • previous thyroid problems
  • infants
  • older adults
  • pregnant people

High iodine levels may also lead to the development of goiter in some people. Goiters are an enlargement of the thyroid that can sometimes be visible in the neck.

A high iodine intake may also cause:

Iodine-induced hyperthyroidism can happen if you are in a high risk group or you’re accidentally consuming more iodine than you realize.

Certain medications, herbal remedies, and nutritional supplements can be quite high in iodine. This includes prenatal vitamins.

Reducing your iodine intake might help correct an overactive thyroid. But it may be several months before your hormone levels begin to normalize.

Also called the “Jod-Basedow effect,” iodine-induced hyperthyroidism is most common in people who previously had iodine deficiency.

As a 2019 clinical review notes, having a history of thyroid disease or iodine deficiency may increase your risk of developing iodine-induced hyperthyroidism in the future. This is due to hyperstimulation of thyroid-stimulating hormones (TSH) that adapt to a previously low iodine intake.

If you have Graves’ disease, a doctor may recommend radioactive iodine. It’s also called radioiodine therapy.

Radioactive iodine therapy works by damaging overactive thyroid cells. The overactive cells absorb most of the iodine in your bloodstream. Any excess amount will leave the body within a few weeks or months.

After treatment, you may develop hypothyroidism. In this case, your doctor will recommend thyroid hormone replacement therapy.

Radioactive iodine is considered safe for people ages 5 years and older. The American Thyroid Association estimates that at least 70% of U.S. adults with a hyperthyroidism diagnosis undergo radioactive iodine therapy.

How much iodine is too much?

Too much iodine can affect your thyroid and lead to other health problems. The National Institutes of Health outlines the daily maximum intake of iodine, based on age group, as follows:

AgeMaximum intake in micrograms (mcg)
0–12 monthsnot established
1–3 years200 mcg
4–8 years300 mcg
9–13 years600 mcg
14–18 years900 mcg
18 years and older1,100 mcg
Was this helpful?

Doctors don’t typically recommend limiting foods high in iodine because they don’t significantly affect the course of hyperthyroidism. But it may be helpful to be aware of high-iodine foods in case of a cumulative effect.

Foods high in iodine include:

  • enriched bread
  • iodized table salt
  • seaweed
  • cod
  • oysters
  • milk
  • yogurt
  • eggs

Talk with a doctor about avoiding other forms of iodine, including potassium iodide or supplements and multivitamins that contain iodine. Over-the-counter medications, such as cough syrups, may also have iodine.

Hyperthyroidism requires treatment to help stop the thyroid gland from producing excessive amounts of hormones. This may be achieved with the following:

Radioactive iodine

Radioactive iodine is an oral treatment that destroys thyroid cells that may be contributing to hyperthyroidism. When used to treat Graves’ disease, hypothyroidism may develop within a few months. Your doctor may prescribe thyroid hormone replacements.

Anti-thyroid drugs

Unlike radioactive iodine, these oral medications don’t destroy thyroid cells. Instead, the goal is to block the thyroid gland’s ability to produce hormones.

Anti-thyroid drugs may not be as effective in managing Graves’ disease. Only about 20–30% of people taking these drugs go into remission.


In some cases, removing one or both sides of the thyroid gland may cure hyperthyroidism. This surgery may be especially helpful for multinodular thyroid diseases.

If your entire thyroid is removed, you will develop hypothyroidism and need lifelong supplemental treatment.


While traditionally used to treat heart arrhythmias, beta-blockers may help improve the symptoms of hyperthyroidism by blocking some of the effects of thyroid hormone on the body, such as nervousness and increased heart rate.

Iodine is a key component of thyroid health. Getting too much or too little of this mineral in your diet can lead to thyroid problems, including hypo and hyperthyroidism.

While Graves’ disease is a common cause of hyperthyroidism, consuming too much iodine can also contribute to an overactive thyroid gland. This is most common in people with a history of iodine deficiency.