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Overview: Iodine is commonly taken to increase iodine levels. Common side effects include diarrhea, nausea, vomiting, rash, or stomach discomfort. Serious side effects are rare but can include thyroid problems or iodine poisoning. Iodine is available over the counter as a supplement and can also be found in multivitamins, prenatal vitamins, and supplements that contain kelp or seaweed. Before taking iodine, tell your health care provider about all of your health conditions and any medicines or supplements you may be using.

Uses

What is iodine used for?

Iodine is commonly used to prevent or treat low iodine levels.

Iodine may also be used for other conditions as determined by your health care provider.

Iodine is available as a dietary supplement in various strengths and dosage forms. Iodine is also found as an ingredient in some multivitamins, prenatal vitamins, and kelp or seaweed supplements.

Note: The FDA has not reviewed iodine for safety and effectiveness. Learn more about dietary supplements here.

Iodine is also available in the form of potassium iodide, a product that is used during nuclear radiation emergencies and for certain long-term lung conditions. See Potassium Iodide for more information.

How does iodine work (mechanism of action)?

Iodine is a mineral that your thyroid uses to make thyroid hormones. These hormones are important for your metabolism and the function of organs in your body. In infants, thyroid hormones play an important role in brain and bone development.

In the United States, most people get enough iodine from their diet. It is found in fish, seaweed, shrimp, milk, yogurt, cheese, and eggs. It is also found in iodized salt. For most adults, the recommended daily intake of iodine is 150 micrograms (mcg). People who are pregnant or breastfeeding need 220-290 mcg of iodine daily. However, some people may not get enough from their diet or have trouble absorbing it. When this happens, you can take iodine supplements to increase your iodine levels.

How should I store iodine?

You should store iodine as directed on the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of iodine?

The most common side effects of iodine are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

  • Diarrhea
  • Nausea or vomiting
  • Rash
  • Swollen or tender salivary glands
  • Stomach pain or discomfort

There may be other side effects of iodine that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of iodine?

While less common, the most serious side effects of iodine are described below, along with what to do if they happen.

Severe Allergic Reactions. Iodine may cause allergic reactions, which can be serious. Stop taking iodine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives, which can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Thyroid Problems. Iodine can cause the function of your thyroid gland to change. This can raise thyroid hormone levels (hyperthyroidism), lower thyroid hormone levels (hypothyroidism), or cause your thyroid to grow larger (thyroid goiter). These problems are more likely to happen when iodine is taken regularly at doses higher than the recommended daily intake. Keep all appointments to have your blood checked. Tell your health care provider if you have any of the following signs of thyroid problems.

  • Weight gain or weight loss
  • Feeling unusually cold or hot
  • Tiredness that does not go away or continues to worsen
  • Mood swings
  • Trouble sleeping
  • Constipation
  • Tightness in your throat
  • A hoarse voice

Iodine Poisoning. People who regularly take large amounts of iodine may have iodine poisoning. This is sometimes called iodism. To reduce the risk of iodine poisoning, do not take more iodine than the recommended daily intake or the amount recommended by your health care provider. Stop taking iodine and call your health care provider right away if you have any of the following symptoms of iodine poisoning.

  • Sore gums or teeth
  • Bad headaches
  • The whites of your eyes seem red
  • Swollen eyelids
  • Blurry vision
  • Your eyes water, your nose runs, or you have more spit in your mouth than usual

Warnings & Precautions

Who should not use iodine?

Allergies to Ingredients. People who are allergic to any of the following should not take iodine.

  • Iodine
  • Iodine/potassium iodide (Lugol’s solution)
  • Potassium iodide
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific iodine products they stock.

What should I know about iodine before using it?

Iodine is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep iodine out of the reach of children.

You can get iodine from several sources, including foods, vitamins, or supplements. Many multivitamin and combination supplement products have iodine in them. It is important not to take too much iodine. Too much iodine can be harmful. If you are not sure how much iodine you need, talk to your health care provider.

Some foods contain chemicals called goitrogens. These chemicals can limit how much iodine your thyroid absorbs. Common foods that contain goitrogens include soy, cabbage, cauliflower, radish, kale, and broccoli. Cooking can reduce the effects of goitrogens on the thyroid, so this is not a problem for most people. But if your diet contains a large amount of these foods and low amounts of iodine, you may be at risk for low iodine levels. Talk to your health care provider if you are unsure whether you are getting enough iodine.

The FDA has not tested iodine products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using iodine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if iodine is right for you.

In particular, make sure that you discuss any of the following.

Low-Iodine Diet. The best sources of iodine in the diet are seafood, dairy, and eggs. People who follow a vegan, seafood-free, or dairy-free diet may be at higher risk for low iodine levels. Talk to your health care provider about whether you should take an iodine supplement.

Thyroid Problems. Taking iodine may change the way your thyroid works. This could make some thyroid problems worse. Tell your health care provider if you have any thyroid problems, such as high or low thyroid hormone levels, thyroid nodules, a thyroid goiter, autoimmune thyroiditis, or Graves’ disease.

Other Current and Past Health Conditions. Tell your health care provider if you have any of the following.

Other Medicines and Supplements. Iodine may interact with other medicines and supplements. Before taking iodine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take iodine (often in prenatal vitamins) while you are pregnant or trying to get pregnant.

Breastfeeding. Iodine is a normal part of breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take iodine while breastfeeding.

Interactions

Does iodine interact with foods or drinks?

There are no known interactions between iodine and foods or drinks.

It is unknown if drinking alcohol will affect iodine.

Does iodine interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking iodine.

  • A thyroid medicine, such as levothyroxine, which is used to raise thyroid hormone levels
  • An antithyroid medicine, such as methimazole or propylthiouracil (PTU), which is used to lower thyroid hormone levels
  • Lithium, which is a medicine for certain mental health conditions
  • Any other product that contains iodine, such as potassium iodide or iodine/potassium iodide (Lugol’s Solution)

The interactions between iodine and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with iodine is incomplete. Always check with your health care provider before taking iodine with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much iodine?

If you or someone else has used too much iodine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Iodine can be found alone in dietary supplements or in combination with other ingredients as part of a multivitamin or prenatal vitamin. Iodine is also found in supplements that contain kelp or seaweed. Read the product label closely and speak with a health care provider about how to take iodine safely. Do not take double or extra doses, even if you miss a dose.