Iodine Supplements For Thyroid Disease

Who might benefit, who might be harmed by taking iodine

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In order to produce hormones, the thyroid needs a trace mineral called iodine. For this reason, alternative health practitioners often advise patients with thyroid disease to take supplements of this essential nutrient—sometimes in megadoses. However, iodine deficiencies are rare in the United States and other developed countries where the mineral is plentiful in iodized salt. It's also found in many common foods—especially seaweed: Most of the Earth's iodine is found in oceans.

In fact, research shows that problems associated with iodine excess occur more frequently than those linked to iodine deficiency. What's more, only if a person's thyroid disease is caused by low levels of iodine would supplements be helpful, but this is hardly ever the case. Ultimately, taking supplemental iodine may cause more problems than it solves.

ways to hit your daily iodine
Illustration by Cindy Chung, Verywell

Health Benefits

Iodine plays a key role in the function of the thyroid, which needs this mineral to produce the thyroid hormones that are key to metabolism, proper bone and brain development of unborn babies and infants, and other important functions. The body doesn't make iodine, so it must come from outside sources.

Prevention and Treatment of Thyroid Disease

Any benefits provided by iodine supplementation would be related to preventing or treating health problems caused by iodine deficiency, particularly hypothyroidism, in which the body makes too little thyroid hormone and goiter—enlargement of the thyroid gland as it tries to produce enough thyroid hormone to keep up with the body's needs, according to the American Thyroid Association (ATA).

During Pregnancy and Breastfeeding

Severe iodine deficiencies in an expectant mom have been associated with miscarriage, stillbirth, and prematurity. Babies born to mothers with iodine deficiency can have congenital abnormalities, intellectual disabilities, and problems with growth, hearing, and speech. The most severe birth defect associated with iodine deficiency during pregnancy is cretinism, a condition marked by permanent brain damage, deafness, inability to speak, small stature, and more.


Supplemental iodine is available in several different forms, each offering widely varying amounts of iodine (and, sometimes, potassium iodide).

It's vital to check with your doctor before you take an iodine supplement to make sure it's advisable and even safe for you and to then read labels carefully so you don't accidentally take too much.

The most common types of iodine supplements include:

Lugol's solution. Developed in 1829 by a French doctor as a potential cure for tuberculosis, Lugol's solution is a combination of 5 percent iodine and 10 percent potassium iodide that currently is used primarily to prepare people with Grave's disease (the main cause of overactive thyroid) for removal of the thyroid gland. It's available over-the-counter

Sea kelp. Kelp is a type of brown seaweed. It's available in tablets, capsules, and other forms to be taken by mouth as an iodine supplement. The amount of iodine in kelp supplements can vary widely—some products may have 150 mcg of iodine per dose while others may have as much as 600 mcg.

The U.S. Food and Drug Administration (FDA) limits daily ingestion of kelp to an amount that provides no more than 225 mcg iodine. The FDA also requires labels on kelp supplements to include this statement:

CAUTION: Do not exceed recommended dosage without first consulting your healthcare practitioner, as excess iodine may adversely affect thyroid function.

Multivitamin/mineral supplements. Most multis that include iodine contain 150 mcg of the mineral, which is 100 percent of the daily value (DV).

Possible Side Effects

Iodine supplements are likely to cause health problems only if taking them leads to an excess of iodine in the body. This is especially true for people who have thyroid disease. Side effects associated with iodine excess that may be caused by taking supplements include:

  • Triggering or worsening of thyroid disease. Studies have found that iodine intake in amounts that are more than adequate or excessive by people with abnormal thyroid function can cause or exacerbate hypothyroidism; goiter; thyroid gland inflammation, autoimmune thyroiditis, and thyroid cancer.
  • Acute iodine poisoning. Toxic amounts of iodine can cause burning of the mouth, throat, and stomach, fever, nausea, vomiting, diarrhea, a weak pulse, cyanosis (a blue or purple tint to the skin caused by too little oxygen in the blood), and coma. It's important to note that iodine toxicity is rare: It would take a very large amount of iodine to bring on these symptoms.
  • Congenital hypothyroidism. Although adequate maternal iodine is essential for fetal and newborn development, there's research to show that if a pregnant or breastfeeding woman gets too much iodine her infant may develop congenital hypothyroidism. In one study, the others of three babies with this condition were found to be taking nutritional supplements that contained iodine levels far above the daily recommended amount.

    Interactions with Food

    Certain foods contain chemicals called goitrogens that sometimes interfere with how well iodine is absorbed by the thyroid. Examples of goitrogen-rich foods include broccoli, bok choy, cabbage, cauliflower, kale, and turnips.

    "For most people in the United States who get adequate amounts of iodine, eating reasonable amounts of foods containing goitrogens is not a concern," according to the NIH.

    Interactions with Medication

    If you're on medication for treating an overactive thyroid, such as Tapazole (methimazole), taking additional iodine in supplement form may lower thyroid function too much.

    Iodine supplements are known to interact or interfere with other medications, especially those listed below. These may not be the only drugs that are affected by iodine—another important reason to check with your doctor before you take iodine.

    • ACE inhibitors (medications for treating high blood pressure), including Lotensin (benazepril) Prinivil or Zestril (lisinopril), and Monopril (fosinopril). Iodine supplements containing potassium iodide could raise the amount of potassium in blood to unsafe levels.
    • Angiotensin receptor blockers (ARBs). These medications for high blood pressure also contain potassium
    • Potassium-sparing diuretics, such as Aldactone (spironolactone) and Midamor (amiloride). The amount of potassium in your blood could become too high if you take potassium iodide with these drugs.
    • Lithium. This drug for treating bipolar disorder is associated with hypothyroidism and goiter, studies have found. High levels of iodine could exacerbate this side effect.


    How much iodine you need each day largely depends on your age and, if you're a woman, whether you're pregnant or breastfeeding. Iodine is measured in micrograms (mcg). These are the daily recommended amounts for iodine, according to the National Institutes of Health Office of Dietary Supplements (ODS).

    Age/Life Stage

    • Birth to 6 months

    • Infants 7-12 months

    • Children 1-8 years

    • Children 9-13 years

    • Teens 14-18 years

    • Adults

    • Pregnant women

    • Breastfeeding women


    • 110 mcg

    • 130 mcg

    • 90 mcg

    • 120 mcg

    • 150 mcg

    • 150 mcg

    • 220 mcg

    • 290 mcg

    Most people in the United States easily reach the recommended levels of iodine in their daily diets. Only people who never use iodized salt may be at risk of a deficiency. However, currently, about 70 percent of households worldwide use iodized salt, according to the ODS.

    The only people who are advised to take iodine supplements are pregnant women, who need about 50 percent more iodine than other women, and those who are breastfeeding. The ATA advises this group to take a daily multivitamin containing 150 mcg of iodine.

    Only about half of multis sold in the U.S. contain iodine, so be sure to read labels or ask your obstetrician or midwife to recommend or prescribe a prenatal vitamin that includes iodine.

    For others, large amounts or long-term use of iodine are possibly unsafe. The upper limits for iodine are as follows:

    • Adults: 1,100 mcg per day
    • Children ages 1 to 3: 200 mcg
    • Children ages 4 to 8: 300 mcg
    • Tweens (ages 9 to 13): 600 mcg
    • Teenagers (ages 14 to 18): 900 mcg

    A Word From Verywell

    Iodine is an essential nutrient for thyroid function, but in the United States and other developed countries, it's extremely rare for someone to have a deficiency. As for people with thyroid disease, it may seem logical that increasing iodine intake through supplementation might be helpful, but in fact, it can be harmful. If you have a thyroid disorder and are being treated by an alternative practitioner who advises you to take iodine supplements, check with your primary care physician or an endocrinologist first.

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