Iodine is a chemical element. The body needs iodine but cannot make it. The needed iodine must come from the diet. As a rule, there is very little iodine in food, unless it has been added during processing, which is now the case with salt. Most of the world’s iodine is found in the ocean, where it is concentrated by sea life, especially seaweed.
The thyroid gland needs iodine to make hormones. If the thyroid doesn’t have enough iodine to do its job, feedback systems in the body cause the thyroid to work harder. This can cause an enlarged thyroid gland (goiter), which becomes evident as a swollen neck.
Other consequences of not having enough iodine (iodine deficiency) are also serious. Iodine deficiency and the resulting low levels of thyroid hormone can cause women to stop ovulating, leading to infertility. Iodine deficiency can also lead to an autoimmune disease of the thyroid and may increase the risk of getting thyroid cancer. Some researchers think that iodine deficiency might also increase the risk of other cancers such as prostate, breast, endometrial, and ovarian cancer.
Iodine deficiency during pregnancy is serious for both the mother and the baby. It can lead to high blood pressure during pregnancy for the mother, and mental retardation for the baby. Iodine plays an important role in development of the central nervous system. In extreme cases, iodine deficiency can lead to cretinism, a disorder that involves severely stunted physical and mental growth.
Iodine deficiency is a common world health problem. The most recognized form of deficiency is goiter. Additionally, across the globe iodine deficiency is thought to be the most common preventable cause of mental retardation. Early in the twentieth century, iodine deficiency was common in the US and Canada, but the addition of iodine to salt has improved public health. The addition of iodine to salt is required in Canada. In the US, iodized salt is not required, but it is widely available. Researchers estimate that iodized salt is used regularly by about half the US population.
Iodine is used to prevent iodine deficiency and its consequences, including goiter. It is also used for treating a skin disease caused by a fungus (cutaneous sporotrichosis); treating fibrocystic breast disease; preventing breast cancer, eye disease, diabetes, and heart disease and stroke; and as an expectorant.
Iodine is also used to for radiation emergencies, to protect the thyroid gland against radioactive iodides. Potassium iodide tablets for use in a radiation emergency are available as FDA-approved products (ThyroShield, Iosat) and on the Internet as food supplements. Potassium iodide should only be used in a radiation emergency, not in advance of an emergency to prevent sickness.
Iodine is applied to the skin to kill germs, prevent soreness inside the mouth (mucositis) caused by chemotherapy, and treat diabetic ulcers.
Iodine is also used for water purification.
How does it work?
Iodine reduces thyroid hormone and can kill fungus, bacteria, and other microorganisms such as amoebas. A specific kind of iodine called potassium iodide is also used to treat (but not prevent) the effects of a radioactive accident.
- Conditions related to too much thyroid gland activity (hyperthyroidism).
- Radiation emergency associated with the use of radioactive iodides.
- Skin infection caused by the fungus Sporothrix (cutaneous sporotrichosis).
Likely Effective for:
- Iodine deficiency. Taking iodine supplements, including iodized salt, is effective for preventing and treating iodine deficiencies.
- Radiation exposure. Taking iodine by mouth is effective for protecting against exposure to radioactive iodides in a radiation emergency.
- Thyroid conditions. Taking iodine by mouth can improve thyroid storm and hyperthyroidism. Also, taking iodized salt in addition to thyroxine after surgery for thyroid disease appears to reduce the size of the thyroid.
- Leg ulcers. Research suggests that applying cadexomer iodine to venous leg ulcers along with compression for 4-6 weeks increases the healing rate. Also, applying povidone-iodine in addition to compression seems help heal leg ulcers and reduce the chance of a future infection.
Possibly Effective for:
- Catheter-related infection. Some evidence suggests that applying povidone-iodine reduces the risk of blood stream infections for people with hemodialysis catheters. However, other research suggests that applying povidone-iodine where a catheter is inserted does not reduce the risk of infection associated with using other types of catheters.
- Conjunctivitis (pinkeye). Research suggests that povidone-iodine solutions are more effective than silver nitrate for decreasing the risk of pinkeye in newborns. However, it is not more effective than the medications erythromycin or chloramphenicol.
- Foot ulcers in diabetes. Applying iodine to foot ulcers might be beneficial for people with foot ulcers related to diabetes.
- Inflammation of the uterus (endometritis). Applying povidone-iodine solution to the vaginal area before a Cesarean delivery reduces the risk of the inflammation of the uterus.
- Painful fibrous breast tissue (fibrocystic breast disease). Research shows that taking iodine, especially molecular iodine, reduces painful fibrous breast tissue.
- Breast pain (mastalgia). Taking iodine tablets daily for 5 months reduces pain and tenderness in women with breast pain related to their menstrual cycle.
- Soreness and swelling inside the mouth. Applying iodine to the skin seems to prevent soreness and swelling inside the mouth caused by chemotherapy.
- Gum infection (periodontitis). Research suggests that rinsing with povidone-iodine during non-surgical treatments for gum infections (periodontitis) can help reduce the depth of infected gum pockets.
- Surgery. Some research suggests that applying povidone-iodine during surgery reduces the risk of infections. However, povidone-iodine seems to be less effective than chlorhexidine at preventing infections at the surgical site.
- Bleeding.Early research suggests that washing the tooth socket with povidone-iodine stops bleeding in more patients after having a tooth pulled compared to saline.
- Chyle in the urine (chyluria). Early research suggests that using povidine-iodine in people with chyle in the urine undergoing a pelvic instillation sclerotherapy may be as effective as standard care.
- Eye infection (corneal ulceration). Early evidence suggests that administering povidone-iodine in addition to standard antibiotic therapy does not improve vision in people with corneal ulcers.
- Fungal skin condition (Cutaneous sporotrichosis). Potassium iodide is commonly used for cutaneous sporotrichosis. There are reports that taking potassium iodide by mouth alone or with another antifungal treatment is effective for most people with cutaneous sporotrichosis.
- Pneumonia. Early research suggests that rinsing the throat with povidone-iodine decreases the risk of pneumonia in people with severe head trauma who are using a ventilator.
- Wound healing. There is some interest in using iodine agents to promote wound healing. While there is some evidence that applying iodine to wounds is more effective than non-antiseptic dressings in reducing wound size, iodine seems to be less effective than antibiotics.
- Other conditions.
Side Effects & Safety
Iodine is LIKELY SAFE for most people when taken by mouth at recommended amounts or when applied to the skin appropriately using approved products.
Iodine can cause significant side effects in some people. Common side effects include nausea and stomach pain, runny nose, headache, metallic taste, and diarrhea.
In sensitive people, iodine can cause side effects including swelling of the lips and face (angioedema), severe bleeding and bruising, fever, joint pain, lymph node enlargement, allergic reactions including hives, and death.
Large amounts or long-term use of iodine are POSSIBLY UNSAFE. Adults should avoid prolonged use of doses higher than 1100 mcg per day (the upper tolerable limit, UL) without proper medical supervision. In children, doses should not exceed 200 mcg per day for children 1 to 3 years old, 300 mcg per day for children 4 to 8 years old, 600 mcg per day for children 9 to 13 years old, and 900 mcg per day for adolescents. These are the upper tolerable limits (UL).
In both children and adults, there is concern that 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, increased saliva, throat inflammation, stomach upset, diarrhea, wasting, depression, skin problems, and many other side effects.
When iodine is used directly on the skin, it can cause skin irritation, stains, allergic reactions, and other side effects. Be careful not to bandage or tightly cover areas that have been treated with iodine to avoid iodine burn.
Special Precautions & Warnings: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). Iodine is POSSIBLY UNSAFE when taken by mouth in high doses. Do not take more than 1100 mcg of iodine per day if you are over 18 years old; do not take more than 900 mcg of iodine per day if you are 14 to 18 years old. Higher intake might cause thyroid problems.
Autoimmune thyroid disease: People with autoimmune thyroid disease may be especially sensitive to the harmful side effects of iodine.
A type of rash called dermatitis herpetiformis: Taking iodine can cause worsening of this rash.
Thyroid disorders, such as too little thyroid function (hypothyroidism), an enlarged thyroid gland (goiter), or a thyroid tumor: Prolonged use or high doses of iodine might make these conditions worse.
Major Interaction Do not take this combination
- Medications for an overactive thyroid (Antithyroid drugs) interacts with IODINE
Iodine can affect the thyroid. Taking iodine along with medications for an overactive thyroid might decrease the thyroid too much. Do not take iodine supplements if you are taking medications for an overactive thyroid.
Some of these medications include methenamine mandelate (Methimazole), methimazole (Tapazole), potassium iodide (Thyro-Block), and others.
Moderate Interaction Be cautious with this combination
- Amiodarone (Cordarone) interacts with IODINE
Amiodarone (Cordarone) contains iodine. Taking iodine supplements along with amiodarone (Cordarone) might cause too much iodine in the blood. Too much iodine in the blood can cause side effects that affect the thyroid.
- Lithium interacts with IODINE
Lithium can inhibit thyroid function. Concomitant use with iodine may have additive or synergistic hypothyroid effects (17574,20754). Monitor thyroid function.
- Medications for high blood pressure (ACE inhibitors) interacts with IODINE
Some medications for high blood pressure might decrease how quickly the body gets rid of potassium. Most iodide supplements contain potassium. Taking potassium iodide along with some medications for high blood pressure might cause too much potassium in the body. Do not take potassium iodide if you are taking medications for high blood pressure.
Some medications for high blood pressure include captopril (Capoten), enalapril (Vasotec), lisinopril (Prinivil, Zestril), ramipril (Altace), and others.
- Medications for high blood pressure (Angiotensin receptor blockers (ARBs)) interacts with IODINE
Some medications for high blood pressure might decrease how quickly the body gets rid of potassium. Most iodine supplements contain potassium. Taking potassium iodide along with some medications for high blood pressure might cause too much potassium in the body. Do not take potassium iodide if you are taking medications for high blood pressure.
The ARBs include losartan (Cozaar), valsartan (Diovan), irbesartan (Avapro), candesartan (Atacand), telmisartan (Micardis), and eprosartan (Teveten).
- Water pills (Potassium-sparing diuretics) interacts with IODINE
Most iodine supplements contain potassium. Some "water pills" might also increase potassium in the body. Taking potassium iodide along with some "water pills" might cause too much potassium to be in the body. Do not take potassium iodide if you are taking "water pills" that increase potassium in the body.
Some "water-pills" that increase potassium in the body include spironolactone (Aldactone), triamterene (Dyrenium), and amiloride (Midamor).
The following doses have been studied in scientific research:
- For radiation emergencies: potassium iodide (KI) should be taken just prior to, or as soon as possible after, exposure. Radiation is most harmful to pregnant or breastfeeding women and children, so KI is dosed according to amount of radiation exposure and age. Radiation exposure is measured in centigrays (cGy). For infants, babies, children, adolescents, and pregnant or breastfeeding women, KI is given if radiation exposure is 5 centigrays (cGy) or more. Tablets can be crushed and mixed with fruit juice, jam, milk, etc.
- For birth through 1 month, the dose is 16 mg of KI;
- For babies and children over 1 month through 3 years, 32 mg;
- For children 3 to 12 years, 65 mg;
- For adolescents 12 through 18 years, 65 mg or 120 mg if the adolescent is approaching adult size;
- For pregnant or breastfeeding women, 120 mg.
- For adults 18 to 40 years with exposure to 10 cGy or more, 130 mg of KI is given.
- For adults over 40 years with exposure to 500 cGy or more, 130 mg of KI is given.
For children and adults, Recommended Dietary Amounts (RDA) have been set: children 1 to 8 years, 90 mcg/day; 9 to 13 years, 120 mcg/day; people age 14 and older, 150 mcg/day. For pregnant women, the RDA is 209 mcg/day, and breastfeeding women, 290 mcg/day.
Tolerable Upper Intake Levels (UL), the highest level of intake that is not likely to cause unwanted side effects, for iodine intake have been set: children 1 to 3 years, 200 mcg/day; 4 to 8 years, 300 mcg/day; 9 to 13 years, 600 mcg/day; 14 to 18 years (including pregnancy and breastfeeding), 900 mcg/day. For adults older than age 19 including pregnant and breastfeeding women, the Tolerable Upper Intake Level is 1100 mcg/day.