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Information on Radiation, Health and the Thyroid,
Including Iodine Testing, Potassium Iodide, and Thyroid Testing


Whether it was the 1986 Chernobyl nuclear disaster, or the post-9/11 fears of nuclear terrorism, or the March 2011, post-tsunami Japanese reactor leaks, concerns about radiation exposure, and its effects on the thyroid, are everpresent.

The thyroid gland, particularly in children, is especially sensitive to the effects of radiation. Diseases of the thyroid -- including thyroid cancer -- are very common and affect tens of millions of people worldwide.

Find out what do you need to know about the thyroid, radiation, thyroid testing, and the use of potassium iodide to help protect against the effects of radiation.

And learn about the ground-breaking "Thyroid Safety Panel" of blood tests that you can order -- whether you're in the United States or around the world -- to evaluate your baseline thyroid function, iodine levels, and identify imbalances now, or in the future.



The Thyroid Safety Test Panel


The March 11, 2011 earthquake, followed by a destructive tsunami, and resulting in severe damage to a number of nuclear reactors in Japan, has caused a serious and ongoing radiation emergency in Japan. As the radiation emergency continues, fear grows that other areas -- including Alaska, Hawaii and the west coast of the United States -- may eventually be exposed to radiation as a result of the Japanese nuclear leak.

The American public's --- and in some cases, the media and practitioners' -- response has been to focus on the over-the-counter supplement, potassium iodide (also known by its chemical symbol KI), which can help prevent radiation-induced thyroid cancer. While adults may benefit from potassium iodide, priority is typically given to administering the supplement to infants, children and pregnant women, who are most susceptible to the thyroid-damaging effects of radiation. The last major radiation emergency of this magnitude was the 1986 Chernobyl accident, when potassium iodide -- which was given to the residents of Poland -- was proven to help that population avoid a spike in thyroid cancer rates. The Ukraine and Russia, however, with no potassium iodide stockpiles or distribution programs in place, have seen huge increases in thyroid cancer rates in the last 25 years.

While potassium iodide can effectively protect the thyroid from radioactive iodine, it has no effect on other types of harmful radiation. It is intended for use only by those who are in the direct path of radiation or fallout, and must be used in the hours before and after the actual radioactive exposure to be effective. There is no benefit to taking potassium iodide outside the window of exposure, taking more than necessary, or taking it for a longer period than specified. Unfortunately, in the fear and frenzy surrounding the Japanese situation, there is not only panic buying of potassium iodide and other iodine supplements, but panic usage of these supplements. This is raising concern among some health officials and advocates.

"I am extremely concerned that we will begin to see a rash of new thyroid problems showing up down the road, as a result of all this unnecessary use of potassium iodide," said Mary Shomon, the New York Times best-selling author of the book "The Thyroid Diet," and an internationally-known thyroid patient advocate. "People outside Japan, who are not in the direct path of fallout, are taking potassium iodide, thinking that they are doing their health a favor. Instead, they may be putting themselves at greater risk of developing thyroid disease. Their thyroid health would be better protected by doing nothing at all right now!!"

Experts recommend that potassium iodide only be taken at recommended dosages by those who are advised by their governmental officials that they are in the direct path of a radioactive plume. Even then, potassium iodide should be taken only in a very specified time before and after the fallout exposure, and according to very specific instructions.

There is reason for caution about taking potassium iodide or iodine supplements, because their unnecessary use can cause conditions such as the Jod-Basedow phenomena, and the Wolff-Chaikoff effect, trigger and/or worsen hyperthyroidism and hypothyroidism, and ultimately cause temporary or even permanent thyroid conditions. It can also cause sialadenitis (an inflammation of the salivary gland), gastrointestinal disturbances, allergic reactions and rashes.

Potassium iodide is also not recommended for those who have had an allergic reaction to iodine, and people with dermatitis herpetiformis and hypocomplementemic vasculitis, conditions that are linked to a risk of iodine sensitivity.

Says Shomon, "While we don't need to rush out and start popping potassium iodide pills, those of us who are not in Japan or directly in the path of any radioactive fallout should consider this as a wake-up call to do three important things to help protect our thyroid health and that of our children. First, I suggest ordering some potassium iodide so that you do have it on hand in the event that there is a local radiation emergency down the road. The FDA-approved forms of potassium iodide are Iosat Tablets, ThyroSafe Tablets, and ThyroShield Solution. Second, consider having baseline thyroid and iodine level tests done for every member of your family via a local physician or through online lab tests. This will allow you to identify undiagnosed thyroid problems now, and monitor changes to your thyroid function over time. And third, learn how to do a thyroid neck check, to monitor for enlargement, lumps or bumps in the gland that can help you detect changes that may signal disease." While many of the FDA-approved formulations of potassium iodide are currently on back-order, as the Japanese situation calms down, they should come back in stock soon. More information is featured here
online.

A baseline panel of thyroid tests may be available through physicians, but for those who want to order their own lab tests online, have the tests run right away, and have results delivered quickly and securely into an online personal health record, the direct-to-consumer laboratory service MyMedLab is available. MyMedLab's "Thyroid Safety Panel" -- developed by Mary Shomon and MyMedLab -- measures Thyroid Stimulating Hormone (TSH), Free T4, Free T3, Thyroid TPO Antibodies, and the Urinary Iodine level -- to establish a baseline of key thyroid health parameters. The Thyroid Safety Panel tests are available through MyMedLab.com and to learn more, please visit: Those who order the test panel also receive exclusive entry to the ThyroidHealth Hub private health group on Facebook, which allows consumers to interact with Mary Shomon and others who have taken the tests, to discuss thyroid health and wellness.

Says Shomon: "We have an estimated 60 million Americans who have thyroid problems, and the majority of them are undiagnosed. Untreated thyroid problems contribute to obesity, heart disease, depression, and a number of other serious health problems that are truly a threat to us today, here and now. I would rather see Americans spend their time and energy safely getting a handle on their thyroid health now, rather than rushing around in a panic trying to find and take potassium iodide that they don't even need, only to discover that they've ended up creating an entirely new thyroid problem for no reason!"

* * *


About MyMedLab: MyMedLab is a privately held company with the primary mission of empowering consumers to make informed health care choices. As a leading provider of direct-to-consumer (DTC) laboratory testing services, MyMedLab has developed a unique suite of software applications and professional networks that enable the ordering, processing, and reporting of test results directly to consumers. This innovative set of services includes access to wellness tests organized by organ and disease profiles, physician oversight of test ordering, educational laboratory content, and results reporting through the web-based platform. In addition to the direct to consumer channel, MyMedLab also offers their software as a subscription service to physician offices or provider organizations developing community outreach programs that incorporate DTC services. For additional information, see http://www.mymedlab.com.

About Mary Shomon: Mary Shomon is an internationally known thyroid patient advocate, and author of ten books on thyroid disease, hormones, and health, including the New York Times bestseller, "The Thyroid Diet." Shomon founded and serves as editor for a number of websites on thyroid disease and hormonal health, including http://www.thyroid-info.com, http://menopausethyroid.com, http://www.thyroidawarenessmonth.com and others. For more than a decade, she has been publishing the popular thyroid patient newsletter, "Sticking Out Our Necks." Shomon is co-founder of the Coalition for Better Thyroid Care, a non-profit organization dedicated to improving thyroid care in the US. Mary Shomon has been featured in hundreds of newspapers, magazines including the Wall Street Journal, First for Women, Elle Magazine, Time magazine, and the New York Times, and on numerous radio and television programs, including ABC World News Tonight, CBS Radio Networks, and National Public Radio.

Where to Get Potassium Iodide

Are you worried about the effect of radiation on your thyroid health?

Whether it was Chernobyl back in the 1980s, the post 9/11 concerns about dirty bombs and terrorist attacks on nuclear plants, or the latest fears in 2011 related to the Japanese nuclear reactor leaks, the effect of radiation on thyroid health is regularly in the news.

If you need to take potassium iodide or other forms of iodine to protect yourself in a radiation emergency, which are the best form to take?

Potassium iodide is made in pill and liquid forms, and the potassium iodide products approved in the U.S. by the Food and Drug Administration are Iosat Tablets (130 mg), ThyroSafe Tablets (65 mg) and ThyroShield Solution (65 mg/ml). Other potassium iodide products can provide similar effectiveness, however.

It's thought that potassium iodide has a shelf life of some 5 to 11 years. After that, it may have somewhat reduced potency or effectiveness, but is still considered safe.

The FDA-approved products are, as of mid-March 2011, generally not available in the U.S. due to shortages. When they are available, online sellers are allowing price gouging, and these potassium iodide preparations are being sold for more than $200 a bottle, which is more than 10 times the usual price for these products.

Check back regularly for links to more products and retailers, as supplies become available.


Life Extension, Potassium Iodide Tablets, 130 mg, 14 Tablets


Source Naturals, Potassium Iodide, 32.5 mg,


Frequently Asked Questions on Potassium Iodide (KI) -- CDC and FDA Fact Sheets

What is Potassium Iodide (KI)?

Potassium iodide (also called KI) is a salt of stable (not radioactive) iodine. Stable iodine is an important chemical needed by the body to make thyroid hormones. Most of the stable iodine in our bodies comes from the food we eat. KI is stable iodine in a medicine form. This fact sheet from the Centers for Disease Control and Prevention (CDC) gives you some basic information about KI. It explains what you should think about before you or a family member takes KI.

What does KI do?

Following a radiological or nuclear event, radioactive iodine may be released into the air and then be breathed into the lungs. Radioactive iodine may also contaminate the local food supply and get into the body through food or through drink. When radioactive materials get into the body through breathing, eating, or drinking, we say that “internal contamination” has occurred. In the case of internal contamination with radioactive iodine, the thyroid gland quickly absorbs this chemical. Radioactive iodine absorbed by the thyroid can then injure the gland. Because non-radioactive KI acts to block radioactive iodine from being taken into the thyroid gland, it can help protect this gland from injury.

What KI cannot do

Knowing what KI cannot do is also important. KI cannot prevent radioactive iodine from entering the body. KI canprotect only the thyroid from radioactive iodine, not other parts of the body. KI cannot reverse the health effects caused by radioactive iodine once damage to the thyroid has occurred. KI cannotprotect the body from radioactive elements other than radioactive iodine—if radioactive iodine is not present, taking KI is not protective.

How does KI work?

The thyroid gland cannot tell the difference between stable and radioactive iodine and will absorb both. KI works by blocking radioactive iodine from entering the thyroid. When a person takes KI, the stable iodine in the medicine gets absorbed by the thyroid. Because KI contains so much stable iodine, the thyroid gland becomes “full” and cannot absorb any more iodine—either stable or radioactive—for the next 24 hours.

Iodized table salt also contains iodine; iodized table salt contains enough iodine to keep most people healthy under normal conditions. However, table salt does not contain enough iodine to block radioactive iodine from getting into your thyroid gland. You should not use table salt as a substitute for KI.

How well does KI work?

Knowing that KI may not give a person 100% protection against radioactive iodine is important. How well KI blocks radioactive iodine depends on

  • how much time passes between contamination with radioactive iodine and the taking of KI (the sooner a person takes KI, the better),
  • how fast KI is absorbed into the blood, and
  • the total amount of radioactive iodine to which a person is exposed.

Who should take KI?

The thyroid glands of a fetus and of an infant are most at risk of injury from radioactive iodine. Young children and people with low stores of iodine in their thyroid are also at risk of thyroid injury.

Infants (including breast-fed infants): Infants need to be given the recommended dosage of KI for babies (see How much KI should I take?). The amount of KI that gets into breast milk is not enough to protect breast-fed infants from exposure to radioactive iodine. The proper dose of KI given to a nursing infant will help protect it from radioactive iodine that it breathes in or drinks in breast milk.

Children: The United States Food and Drug Administration (FDA) recommends that all children internally contaminated with (or likely to be internally contaminated with) radioactive iodine take KI, unless they have known allergies to iodine. Children from newborn to 18 years of age are the most sensitive to the potentially harmful effects of radioactive iodine.

Young Adults: The FDA recommends that young adults (between the ages of 18 and 40 years) internally contaminated with (or likely to be internally contaminated with) radioactive iodine take the recommended dose of KI. Young adults are less sensitive to the effects of radioactive iodine than are children.

Pregnant Women: Because all forms of iodine cross the placenta, pregnant women should take KI to protect the growing fetus. However, pregnant women should take only one dose of KI following internal contamination with (or likely internal contamination with) radioactive iodine.

Breastfeeding Women: Women who are breastfeeding should take only one dose of KI if they have been internally contaminated with (or are likely to be internally contaminated with) radioactive iodine. Because radioactive iodine quickly gets into breast milk, CDC recommends that women internally contaminated with (or are likely to be internally contaminated with) radioactive iodine stop breastfeeding and feed their child baby formula or other food if it is available. If breast milk is the only food available for an infant, nursing should continue.

Adults: Adults older than 40 years should not take KI unless public health or emergency management officials say that contamination with a very large dose of radioactive iodine is expected. Adults older than 40 years have the lowest chance of developing thyroid cancer or thyroid injury after contamination with radioactive iodine. They also have a greater chance of having allergic reactions to KI.

When should I take KI?

After a radiologic or nuclear event, local public health or emergency management officials will tell the public if KI or other protective actions are needed. For example, public health officials may advise you to remain in your home, school, or place of work (this is known as “shelter-in-place”) or to evacuate. You may also be told not to eat some foods and not to drink some beverages until a safe supply can be brought in from outside the affected area. Following the instructions given to you by these authorities can lower the amount of radioactive iodine that enters your body and lower the risk of serious injury to your thyroid gland.

How much KI should I take?

The FDA has approved two different forms of KI—tablets and liquid—that people can take by mouth after a nuclear radiation emergency. Tablets come in two strengths, 130 milligram (mg) and 65 mg. The tablets are scored so they may be cut into smaller pieces for lower doses. Each milliliter (mL) of the oral liquid solution contains 65 mg of KI.
According to the FDA, the following doses are appropriate to take after internal contamination with (or likely internal contamination with) radioactive iodine:

  • Adults should take 130 mg (one 130 mg tablet OR two 65 mg tablets OR two mL of solution).
  • Women who are breastfeeding should take the adult dose of 130 mg.
  • Children between 3 and 18 years of age should take 65 mg (one 65 mg tablet OR 1 mL of solution). Children who are adult size (greater than or equal to 150 pounds) should take the full adult dose, regardless of their age.
  • Infants and children between 1 month and 3 years of age should take 32 mg (½ of a 65 mg tablet OR ½ mL of solution). This dose is for both nursing and non-nursing infants and children.
  • Newborns from birth to 1 month of age should be given 16 mg (¼ of a 65 mg tablet or ¼ mL of solution). This dose is for both nursing and non-nursing newborn infants.

How often should I take KI?

A single dose of KI protects the thyroid gland for 24 hours. A one-time dose at the levels recommended in this fact sheet is usually all that is needed to protect the thyroid gland. In some cases, radioactive iodine might be in the environment for more than 24 hours. If that happens, local emergency management or public health officials may tell you to take one dose of KI every 24 hours for a few days. You should do this only on the advice of emergency management officials, public health officials, or your doctor. Avoid repeat dosing with KI for pregnant and breastfeeding women and newborn infants. Those individuals may need to be evacuated until levels of radioactive iodine in the environment fall.

Taking a higher dose of KI, or taking KI more often than recommended, does not offer more protection and can cause severe illness or death.

Medical conditions that may make it harmful to take KI

Taking KI may be harmful for some people because of the high levels of iodine in this medicine. You should not take KI if
• you know you are allergic to iodine (If you are unsure about this, consult your doctor. A seafood or shellfish allergy does not necessarily mean that you are allergic to iodine.) or
• you have certain skin disorders (such as dermatitis herpetiformis or urticaria vasculitis).

People with thyroid disease (for example, multinodular goiter, Graves' disease, or autoimmune thyroiditis) may be treated with KI. This should happen under careful supervision of a doctor, especially if dosing lasts for more than a few days.

In all cases, talk to your doctor if you are not sure whether to take KI.

What are the possible risks and side effects of KI?

When public health or emergency management officials tell the public to take KI following a radiologic or nuclear event, the benefits of taking this drug outweigh the risks. This is true for all age groups. Some general side effects caused by KI may include intestinal upset, allergic reactions (possibly severe), rashes, and inflammation of the salivary glands.

When taken as recommended, KI causes only rare adverse health effects that specifically involve the thyroid gland. In general, you are more likely to have an adverse health effect involving the thyroid gland if you

  • take a higher than recommended dose of KI,
  • take the drug for several days, or
  • have pre-existing thyroid disease.

Newborn infants (less than 1 month old) who receive more than one dose of KI are at particular risk for developing a condition known as hypothyroidism (thyroid hormone levels that are too low). If not treated, hypothyroidism can cause brain damage. Infants who receive KI should have their thyroid hormone levels checked and monitored by a doctor. Avoid repeat dosing of KI to newborns.

Where can I get KI?

KI is available without a prescription. You should talk to your pharmacist to get KI and for directions about how to take it correctly. Your pharmacist can sell you KI brands that have been approved by the FDA.





In December 2001, the Food and Drug Administration (FDA) issued a final Guidance on Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies. The objective of the document is to provide guidance to other Federal agencies, including the Environmental Protection Agency (EPA) and the Nuclear Regulatory Commission (NRC), and to state and local governments regarding the safe and effective use of potassium iodide (KI) as an adjunct to other public health protective measures in the event that radioactive iodine is released into the environment. The adoption and implementation of the recommendations are at the discretion of the state and local governments responsible for developing regional emergency-response plans related to radiation emergencies. The recommendations in the guidance address KI dosage and the projected radiation exposure at which the drug should be used. This guidance updates FDA's 1982 recommendations.

1.  What does potassium iodide (KI) do?

The effectiveness of KI as a specific blocker of thyroid radioiodine uptake is well established. When administered in the recommended dose, KI is effective in reducing the risk of thyroid cancer in individuals or populations at risk for inhalation or ingestion of radioiodines. KI floods the thyroid with non-radioactive iodine and prevents the uptake of the radioactive molecules, which are subsequently excreted in the urine.

2.  Can potassium iodide (KI) be used to protect against radiation from bombs other than radioactive iodine?

Potassium iodide ( KI) works only to prevent the thyroid from uptaking radioactive iodine. It is not a general radioprotective agent.

3.  Who really needs to take potassium iodide (KI) after a nuclear radiation release?

The FDA guidance prioritizes groups based on age, which primarily determines risk for radioiodine-induced thyroid cancer.  Those at highest risk are infants and children, as well as pregnant and nursing females, and the recommendation is to treat them at the lowest threshold (with respect to predicted radioactive dose to the thyroid).  Anyone over age 18 and up to age 40 should be treated at a slightly higher threshold.  Finally, anyone over 40 should be treated with KI only if the predicted exposure is high enough to destroy the thyroid and induce lifelong hypothyroidism (thyroid deficiency).

4.  What potassium iodide (KI) products are currently available? 

As of January 2005, Iosat, ThyroSafe, and ThyroShield are FDA approved KI products. You can find out more about these products at Drugs@FDA. Please be aware that only the KI products approved by FDA may be legally marketed in the United States.

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5.  How are these products available?

In addition to distributing to state, local and federal agencies, Anbex, Inc., has made Iosat Tablets (130 mg) available to the general public via the Internet. For further information on KI products, you can contact these companies as noted below:

6.  What dosages of potassium iodide (KI) should be taken for specific exposure levels?

Exposures greater than 5 cGy:   
    Birth through 1 mo.  - 16 mg.
    1 mo. through 3 yrs.  - 32 mg.
    3 yrs through 18 yrs.  - 65 mg. (Adolescents>150 pounds should take adult dose.)

Exposures greater than 10 cGy: 
    18 yrs through 40 yrs. - 130 mg

Exposures greater than 500 cGy: 
    Adults over 40 yrs - 130 mg.

7.  How long should potassium iodide (KI) be taken?

Since KI protects for approximately 24 hours, it should be dosed daily until the risk no longer exists.  Priority with regard to evacuation and sheltering should be given to pregnant females and neonates because of the potential for KI to suppress thyroid function in the fetus and neonate.  Unless other protective measures are not available, we do not recommend repeat dosing in pregnant females and neonates.

8.  Who should not take potassium iodide (KI) or have restricted use?

Persons with known iodine sensitivity should avoid KI, as should individuals with dermatitis herpetiformis and hypocomplementemic vasculitis, extremely rare conditions associated with an increased risk of iodine hypersensitivity. Individuals with multinodular goiter, Graves' disease, and autoimmune thyroiditis should be treated with caution -- especially if dosing extends beyond a few days.

9.  What are the possible risks and side effects of taking potassium iodide (KI)?

Thyroidal side effects of KI at recommended doses rarely occur in iodine-sufficient populations such as the U.S. As a rule, the risk of thyroidal side effects is related to dose and to the presence of underlying thyroid disease (e.g., goiter, thyroiditis, Graves').  FDA recommends adherence to the Guidance on Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies for intervention threshold and dose, though we recognize that the exigencies of any particular emergency situation may mandate deviations from those recommendations. With that in mind, it should be understood that as a general rule, the risks of KI are far outweighed by the benefits with regard to prevention of thyroid cancer in susceptible individuals.

10.  Should I check with my doctor first?

Potassium iodide (KI) is available over-the-counter (OTC).  However, if you have any health concerns or questions, you should check with your doctor.

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11.  As a doctor, should I be recommending potassium iodide (KI) for my patients who request it?

As with any drug, physicians should understand the risks and benefits of KI before recommending it or prescribing it to patients. We recommend that physicians read our guidance for more information. It is available on the FDA Drug Guidances web page, under procedural guidance #18. The FDA guidance discusses the rationale and methods of safe and effective use of KI in radiation emergencies. It specifically addresses threshold predicted thyroid radioiodine exposure for intervention and dosing by age group. The recommendations for intervention are based on categories of risk for thyroid cancer, with the young prioritized because of increased sensitivity to the carcinogenic effects of radioiodine.

12.  Should I go out and buy potassium iodide (KI) to keep on hand?

KI works best if used within 3-4 hours of exposure. Although FDA has not made specific recommendations for individual purchase or use of KI, the Nuclear Regulatory Commission has contracted to purchase KI for states with nuclear reactors and states that have population within the 10-mile emergency planning zone, e.g., Delaware or West Virginia.

13.  How do I know that potassium iodide (KI) will be available in case of an emergency?

FDA will continue to work with interested pharmaceutical manufacturers to assure that high quality, safe, and effective KI products are available for purchase by consumers, by state and local authorities, and by federal government agencies electing to do so.



Other Key Resources on Potassium Iodide






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Mary Shomon, Editor/Webmaster, P.O. Box 565, Kensington, MD 20895-0565.

All information is intended for your general knowledge only and is not a substitute for medical advice or treatment for specific medical conditions. You should seek prompt medical care for any specific health issues and consult your physician or health practitioner before starting or changing any aspect of your medical treatment, diet or fitness regimen. Please see our full disclaimer.