Overview

Iodine is an element that is used by the thyroid. Humans cannot produce iodine, so it must be consumed. It is added to some foods and also to salt.

Iodine reduces thyroid hormone and can kill fungus, bacteria, and other microorganisms such as amoebas. Iodine deficiency is one of the most common and preventable world health problems. Most iodine is found in the ocean, where it is concentrated by sea life, particularly in seaweed.

Iodine is taken by mouth to prevent and treat iodine deficiency and its consequences, including goiter and some thyroid disorders. A specific kind of iodine called potassium iodide is also US FDA approved to prevent thyroid damage after a radioactive accident. Iodine is also used for pink eye, gum infections, wound healing, and many other conditions, but there is limited scientific evidence to support many of these uses.

Uses & Effectiveness

Likely Effective for

  • Iodine deficiency. Taking iodine supplements by mouth, including iodized salt, is effective for preventing and treating iodine deficiency.
  • Radiation exposure. Taking iodine by mouth can protect the thyroid after exposure in a radiation emergency. But it should not be used for general protection against radiation.

Possibly Effective for

  • Pink eye. Using eye drops containing iodine in the form of povidone-iodine seems to reduce the risk of pink eye in newborns. It also seems to help treat pink eye in adults.
  • Foot sores in people with diabetes. Applying iodine to foot sores might help treat foot ulcers related to diabetes.
  • Swelling (inflammation) of the lining of the uterus (endometritis). Washing the vagina with a solution containing iodine in the form of povidone-iodine before a cesarean delivery reduces the risk of swelling of the uterus lining.
  • A type of benign (non-cancerous) breast disease (fibrocystic breast disease). Taking molecular iodine, in a dose of about 3000-6000 mcg daily, reduces breast tenderness and pain. Lower doses of 1500 mcg daily don't seem to help.
  • Swelling (inflammation) and sores inside the mouth (oral mucositis). Rinsing the mouth with an iodine solution seems to prevent soreness and swelling inside the mouth caused by chemotherapy.
  • A serious gum infection (periodontitis). Rinsing the mouth with an iodine solution during non-surgical treatments for gum infections can help reduce the depth of infected gum pockets.
  • Infection after surgery. Applying iodine in the form of povidone-iodine before or during surgery reduces the risk of infections. But it's unclear how it compares to other options, such as chlorhexidine, for preventing infections.
  • A life-threatening condition caused by excess of thyroid hormone (thyroid storm). Taking iodine by mouth in combination with other treatments can help treat thyroid storm.
  • Lumps in the thyroid. Taking iodine by mouth can improve lumps on the thyroid called thyroid nodules.
  • Leg sores caused by weak blood circulation (venous leg ulcer). Applying cadexomer iodine to the skin might help leg ulcers heal. But it's unclear if applying povidone-iodine helps.

Possibly Ineffective for

  • Infections in people with catheters. Applying povidone-iodine where a dialysis catheter is inserted doesn't seem to work as well as chlorhexidine for reducing the risk of a blood infection. Applying povidone-iodine before inserting a urinary catheter doesn't reduce the risk for infection.
  • Growth and development in premature infants. Feeding premature infants iodine supplements doesn't improve their brain development nor reduce their risk of dying.

There is interest in using iodine for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.

Side Effects

When taken by mouth: Iodine is likely safe for most people when taken in doses less than 1100 mcg daily. Large amounts or long-term use of iodine is possibly unsafe. Adults should avoid prolonged use of higher doses without proper medical supervision. Higher intake can increase the risk of side effects such as thyroid problems. Iodine in larger amounts can cause metallic taste, soreness of teeth and gums, burning in mouth and throat, stomach upset, and many other side effects.

When applied to the skin: Iodine is likely safe for most people when appropriately diluted products are used. A 2% iodine solution is an FDA-approved prescription product.

Special Precautions and Warnings

When taken by mouth: Iodine is likely safe for most people when taken in doses less than 1100 mcg daily. Large amounts or long-term use of iodine is possibly unsafe. Adults should avoid prolonged use of higher doses without proper medical supervision. Higher intake can increase the risk of side effects such as thyroid problems. Iodine in larger amounts can cause metallic taste, soreness of teeth and gums, burning in mouth and throat, stomach upset, and many other side effects.

When applied to the skin: Iodine is likely safe for most people when appropriately diluted products are used. A 2% iodine solution is an FDA-approved prescription product.

Pregnancy and breast-feeding: Iodine is likely safe when taken by mouth in recommended amounts or when applied to the skin appropriately using an approved product (2% solution). Do not take more than 1100 mcg of iodine daily if you are over 18 years old; do not take more than 900 mcg of iodine daily if you are 14-18 years old. Iodine is possibly unsafe when taken by mouth in high doses. Higher intake might cause thyroid problems in the baby.

Children: Iodine is likely safe when taken by mouth in appropriate doses depending on age. Doses should not exceed 200 mcg daily for children 1 to 3 years old, 300 mcg daily for children 4 to 8 years old, 600 mcg daily for children 9 to 13 years old, and 900 mcg per day for adolescents.

A type of rash called dermatitis herpetiformis: Taking iodine can make this rash worse.

Thyroid disorders: Prolonged use or high doses of iodine might make certain thyroid disorders worse, including hypothyroidism, an enlarged thyroid gland (goiter), or a thyroid tumor. Also, people with autoimmune thyroid disease might be especially sensitive to the harmful effects of iodine.

Interactions

    Moderate Interaction

    Be cautious with this combination

  • Amiodarone (Cordarone) interacts with Iodine

    Amiodarone contains iodine. Taking iodine supplements along with amiodarone might increase the levels of iodine in the blood. Too much iodine in the blood can cause side effects that affect the thyroid.

  • Lithium interacts with Iodine

    Large amounts of iodine can decrease thyroid function. Lithium can also decrease thyroid function. Taking iodine along with lithium might decrease thyroid function too much. Do not take large amounts of iodine if you are taking lithium.

  • Medications for an overactive thyroid (Antithyroid drugs) interacts with Iodine

    Iodine can increase or decrease thyroid function. Taking iodine along with medications for an overactive thyroid might change the effects of these medications. Do not take iodine supplements if you are taking medications for an overactive thyroid, unless recommended by a healthcare provider.

Dosing

Iodine is an essential nutrient found in iodized salt, marine products such as seaweed, as well as eggs and cow's milk. The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). For adults, the RDA is 150 mcg daily. While pregnant, the RDA is 220 mcg daily. While breast-feeding, the RDA is 290 mcg daily. In children, the RDA depends on age.

Iodine is also available in supplements and in various topical solutions, eye drops, mouthwashes, ointments, and scrubs. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.
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