Using Potassium Iodide Following a Nuclear Incident

Avatar Gaye Levy  |  Updated: December 16, 2020
Using Potassium Iodide Following a Nuclear Incident

Much has been speculated by sources a lot more knowledgeable than me on the effect of radiation to North America – and specifically the Pacific coast – if a fuel pool at Fukushima collapses. Some of these sources are scientists while others are pure speculators. The truth, most likely, will fall somewhere in between.

Let me say this at the onset. I do not claim to be an expert on radiation and I am not a medical professional. I am, however, someone who wants to prepare for the worst, weather it means making lifestyle changes or taking preventative measures after the fact.

A Primer on Using Potassium Iodide

To that end, I have tried to educate myself on the ins and outs of potassium iodide which is widely advertised to the prepper community as something to have on hand and in our bug-out-bags. And yes, I do have some myself but other than the leaflet that comes with the package, my own knowledge of KI (the chemical symbol for potassium iodide) is next to none.

Today I submit the results of my research regarding the safe use if potassium iodide along with a list of resources you can use in your own investigation of tactics to follow if and when there is a nuclear incident in your area.

It is All About the Thyroid Gland

The thyroid gland uses iodine to produce hormones that regulate the body’s metabolism. The problem, as I understand it, is that the thyroid gland will use any iodine that is in a person’s bloodstream and cannot tell the difference between radioactive and non-radioactive forms of iodine. If radioactive iodine is absorbed, energy in the form of radiation is released back into the thyroid in high concentrations. This energy can damage the cells of the thyroid and may lead to thyroid cancer or other diseases of the thyroid.

thyroid gland

In the event of a nuclear incident, such as a meltdown at Fukushima or an accident at a nearby nuclear plant, a large amount of radioactive iodine will be released into the air. If this were to happen, potassium iodide would be used to protect, or block, the thyroid from irradiation. Commonly known as “thyroid blocking”, taking potassium iodide before or at the beginning of exposure to radioactive iodine will block the uptake of radioactive iodine.

What Is Potassium Iodide?

Potassium iodide (KI) is a salt of stable iodine that can help block radioactive iodine from being absorbed by the thyroid gland, thus protecting it from radiation injury. According to the FDA:

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.

So what does this mean? Stable, non-radioactive iodine in the Potassium Iodide pill will load up the thyroid gland so that there is no space left for the radioactive iodine to be absorbed. The harmful radioactive iodine will then harmlessly be excreted from the body through the kidneys as waste.

What About Risks and Side Effects?

There may be side affects to taking potassium iodide. Some of these side effects are skin rashes, swelling of the salivary glands, a burning sensation in the mouth and throat, sore teeth and gums, symptoms of a head cold, an upset stomach and diarrhea.

People who are allergic to iodine should not take potassium iodide. In addition, people who have certain thyroid conditions (such as Graves’ disease, other autoimmune thyroid diseases, and/or a goiter) should be very careful when taking it. Persons allergic to shellfish could potentially be allergic to potassium iodide as well.

I can not stress this enough: if you are allergic to iodine or shellfish, or have a thyroid disorder, speak with a trusted medical professional to discuss alternatives to potassium iodide.

What is the Proper Dosage?

The US Food and Drug Administration (FDA) has set recommended dosages for individuals based on age.

Less than 1 month old – 16 mg
1 month to 3 years – 32 mg
3 to 18 years – 65 mg
Over 18 years or 150 lbs – 130 mg

According to The Survival Medicine Handbook (my survival medicine bible):

Take the KI tablet once a day for 7-10 days, or longer if prolonged or multiple exposures are expected. Children should take 1/2 doses. It is also recommended to consider 1/2 tablets for large dogs and 1/4 tablet for small dogs and cats.

Update: This reference is referring to the 130 mg tablet. 1/2 = 65 mg.

When should Potassium Iodide be taken?

Potassium iodide should only be taken when directed by public health officials. If there is a public health emergency, you will want to listen to television or radio broadcasts for information and instructions on how best to protect yourself and your loved ones.

Two points. First, you want to have a working emergency radio that will operate work on battery in the event the grid is down and traditional power sources are unavailable. Second, you want your own supply of potassium iodide so you are not dependent on the government to come around and give you some – or worse – having to stand in line at the pharmacy or other hand-out station.

It is important to note that if a nuclear incident occurs, officials will first determine which radioactive substances are involved before recommending that people take potassium iodide. Potassium iodide will only be recommended when there are significant amounts of radioactive iodine in the air. If radioactive iodine is not present, then taking potassium iodide will not protect you.

If radioactive iodine is present, potassium iodide works best when taken before (about one-half hour) or at the same time of exposure to radioactive iodine. Potassium iodide can still offer some protection even if taken up to 3 hours or longer after exposure.

What is the Shelf Life of KI tablets?

According to the US Nuclear Regulatory Commission:

The manufacturer’s of Potassium Iodide must specify an expiration date of the drug on either the package or the individually wrapped tablet. The NRC distributes two tablet strengths of potassium iodide, 130 and 65 mg tablets. The shelf life of IOSAT 130 mg tablets is 7 years and the shelf life of ThyroSafe 65 mg tablets is 6 years.

Potassium iodide tablets are inherently stable and do not lose their effectiveness over time. Manufacturers must label their products with a shelf-life to ensure that consumers purchase safe and useful products.

My opinion, for what it is worth, is that I would rather have fresh potassium iodide tablets in my personal preparedness kit. They are inexpensive enough so why take a chance?

Where to Buy Potassium Iodide

Potassium iodide is commonly available over-the-counter although some pharmacies may have to order it for you. Amazon , Emergency Essentials and other online vendors carry potassium iodide. Be aware that to the best of my knowledge, the FDA has only approved Iosat, ThyroSafe, and ThyroShield for over the counter sale in the United States.

potassium iodide

Note: the size of each tablet will be noted on the package. My package of ThyroSafe, as an example, indicates there are 20 tablets, 65 milligrams each. I also have a package from LifeExtension that contains 14 tables, 130 milligrams each.

What Other Dangers Are Out There?

In addition to radioactive iodine, in a catastrophic nuclear incident there are major health risks with Cesium-137. The scary part is the Cesium-137 is lightweight and can be carried long distances by the wind and ocean currents.

There are some studies that indicate that calcium, potassium and iron supplements (and foods rich in these minerals) will help replace Cesium-137 in the body. Whether that is true or not, it might not be a bad idea to keep some on hand and supplement-up if necessary.

Nine Things You Can Do Now to Reduce the Risk of Radiation Exposure

1. Build up your immune system by consuming a diet rich in antioxidants.

2. Avoid, or better yet, eliminate the consumption of seafood caught in the Pacific north of the equator. The same applies to seafood from parts unknown.

3. If you know something is coming (such as a plume crossing the Pacific), be proactive and load up on the supplements calcium, potassium and magnesium.

4. Likewise, if something is heading your way, take off your shoes before going inside (and leave them outdoors). This will prevent tracking miniscule particles into your home.

5. Wash your hands and kitchen surfaces often.

6. Always wash food before cooking or eating raw. Rinse all cans, bottles and jars before opening them; and rinse the can opener as well.

7. Wipe pets’ feet with a damp cloth before or right after they come inside.

8. Vacuum soft surfaces frequently with a HEPA vacuums to remove excess dust and also damp mop hard surfaces daily. Don’t dust surfaces. Instead, wipe them using a damp cloth.

9. If exposure is suspected, close all windows and keep them closed. Stay inside and keep up the vacuuming and mopping.

Summing It All Up

The use of potassium iodide will not not protect you from inhaling or ingesting radioactive materials released to the environment. It will, however, “fill” the thyroid with non-radioactive iodine thus preventing the bad stuff from taking over and causing thyroid cancer. It is not an “anti-radiation” pill and it will not protect you from external radiation exposure or from other radioactive substances such as radioactive cesium.

That said, having a supply of potassium iodide available for your family as insurance makes good sense much the same way as having bandages, antibiotics, trauma items, suture kits makes sense.

The Final Word

This article began as a project to research how potassium iodide worked and also to answer some of my own questions regarding dosages, side effects, shelf life and other considerations. I hope that in some small way the information I have gathered on potassium iodide has answered some of your own questions and, further, that it motivates you to be ready, if and when your are put in the path of a radiological or nuclear incident.


The information I have gathered in this article is for general informational purposes only. Living in the Pacific Northwest and on the water, I am keenly aware of the potential for radiation exposure from Fukushima or, for that matter, a mishap in the ongoing cleanup effort at the Hanford site in Eastern Washington. Regardless of my own concerns, you should consult with your doctor or other qualified health care provider before making any decisions about whether to take potassium iodide or the supplements mentioned in the article.


US FDA Frequently Asked Questions on Potassium Iodide (KI)
NY City Department of Health
US NRC Frequently Asked Questions About Potassium Iodide
Medline Plus: Potassium Iodide
WHO: Use of potassium iodide for thyroid protection during nuclear or radiological emergencies
Home Health Physics (Joy and and Randall Thompson and David Bear)
How to Reduce Your Risk of Radiation from Fukushima
The Survival Medicine Handbook

Enjoy your next adventure through common sense and thoughtful preparation!

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From the Bargain Bin: When it comes to protection from radiation, a few things should be on hand. Here are some ideas to get you started.

iOSAT Potassium Iodide Tablets, 130 mg (14 Tablets): These were backordered for weeks and highly inflated price-wise after Fukushima. Be sure to get a package now for each family member. The way these tabs work is that they fill the thyroid gland with potassium iodide, thus reducing the chance that harmful radioactive iodine will enter and cause sickness or cancer.

NukAlert: Radiation Detector/Monitor:The NukAlert is a personal radiation meter, monitor and alarm that will promptly warn you of the presence of dangerous levels of radiation. It is designed to be attached to a key chain so that you can keep it with you at all times.

Ambient Weather WR-089 Compact Emergency Solar Hand Crank AM/FM/NOAA Weather Radio, Flashlight, Smart Phone Charger with Cables: This reasonably priced radio is popular with Backdoor Survival readers.

N100 Respirator Masks: You want the N100 respirator masks and not the less effective N95 masks. These two were in great demand after Fukushima so if you did not pick up a pack or two then, get them now. This Moldex 2730 is NIOSH certified to have a filter efficiency of 99.97% or greater against particulate aerosols free of oil.

RADSticker nuclear radiation exposure determining dosimeter: The purpose of these stickers is to provide timely personal radiation exposure information in an event of an accident at a nuclear power plant or a nuclear or dirty bomb explosion. Low in cost, the RADSticker will help you determine whether you will need for medical treatment.

3M Duct Tape: Duct tape is an absolute necessity when sealing off a space to shelter in place. For this purpose you want something better than the cheap stuff you get at the dollar store.

Emergency Air for Shelter-In-Place Preppers and Home Built Bunkers: Sheltering in place by sealing in a room is problematic at best since your supply of breathable air is limited. The system detailed in this book allows anyone to breathe safely while under threat and while following FEMA guidelines for sheltering-in-place.



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25 Responses to “Using Potassium Iodide Following a Nuclear Incident”

  1. Was reading your article and feeling self satisfied since I have enough of the potassium iodite on hand to treat several people. THEN I came across your warning about allergies to shell fish and it was like a great awakening. I had once seriously pigged out on shell fish, we had clams, oysters, shirmp and scallops, all in one meal, and I had had such a bad reaction that I had had to go to the ER where they gave me an IV injection of Benedryl (which is horrible in itself). I have eaten fish before and after many times with no adverse reaction, and had pretty well forgotten that one horrible incident. I am glad your article reminded me of that and will ask my doctor’s advice about the safety of me taking this medicine before I do so. You just might have saved my life, where I live even under the best of situations medical care is very difficult to come by, and in an emergency situation the last thing I would need would be to self inflict a life threatening allergic reaction. It had not even crossed my mind Until I read your article this morning. Thank you, thank you, thank you over and over.

  2. Oh my gosh – I am so glad I took the time to write up my research on potassium iodide. I did it for my own benefit but like much of what I do, I tend to share what I learn along the way. Sometimes what I have to say is pretty basic and simplistic but in this case, yes, it can help prevent a major life threatening drug reaction.

    Please share this information with anyone who will listen and espescially encourage people to check with their doctors now, which I hope is well in advance of any need to take KI.

  3. Great article and good information. Thank you!

    One note – you said: “Let me say this at the onset. I do claim to be an expert on radiation and I am not a medical professional.”
    I think you meant to say “I do NOT claim …” – may want to correct it.

  4. One question. I have noticed several companies are selling potassium iodate. What is the difference, and does potassium iodate work as well as potassium iodide? I also noticed the iodate form seems to be less expensive.

    • KI = potassium iodide
      KOI3 = potassium iodate

      Here is an article that covers the basics pretty well. The issue when using KI or KI)3 as a prophylactic against radioiodine is there is more iodine available biologically in KI than KIO3. However one would simply need to take more KIO3 vs KI to make up the difference.


      It is important to note, KI is useless unless the nuclear accident has recently occurred. You must take KI or KIO3 PRIOR to exposure or its effects are reduced significantly after only 4 hours.

      Here is another article that notes if you are over age 40, you can skip the KI:


    • Unfortunately, there’s a typo in that. Here’s a list of the various possibilities, in order of increasing oxygen:-

      – KI = potassium iodide;
      – KIO = potassium hypoiodite (this is an analogue of household bleach, NaClO or sodium hypochlorite);
      – KIO2 = potassium iodite (which is worth mentioning as the first comment, from geena, might have meant that if it wasn’t a typo);
      – KIO3 = potassium iodate;
      – KIO4 = potassium periodate.

  5. I read a comment somewhere that said iodine for protecting against radioactivity is not needed by those over 40 yrs old.
    I don’t know if there’s any truth to that claim.

    I’ve been reading about taking iodine in the form of kelp tablets, is that similar to other iodine or the least bit helpful to protect against radiation? My understanding is, once the thyroid is full of iodine, that’s all it will take in. But I’m not well versed on the subject.

    Also, I’ve read that when taking iodine or kelp tablets a person should also take selenium to balance things out or problems occur. Would taking selenium be beneficial if you took iodine for radiation protection? I don’t know enough to say.

    I found an olive leaf capsule that says it has selenium in it. If that’s helpful to anyone? Sorry, I don’t recall the brand name at the moment.

    • In my research, I learned that younger people and children are more susceptible to thyroid cancer but that does not mean that adults are immune. OTOH, if we get into a rationing situation, my guess is that those of us older 40 will be left out.

      This is a quote from Seattle Children’s Hospital:

      “Is Radiation Worse For Kids? Yes. After studying the effects of the A-bomb in Japan and the fallout from Chernobyl, we know that children are much more vulnerable to the effects of radiation, partly because they absorb and metabolize substances differently and because they are closer and interact more with the ground, where fallout would settle. Further, because of high concentrations in cow’s milk, children (big milk drinkers) are at increased risk. Ultimately, radiation can damage cells in the body. Therefore, we always want to reduce any radiation exposures, particularly in kids.”

      Here is a link: //

      I don’t know the answer about kelp (and seaweed for that matter) but as I recall, Joy Thompson mentioned something about kelp in her comments. Something else to look into . . .

    • Children are more susceptible to the damaging effects of ionizing radiation because their cells are still rapidly dividing (they are growing).

    • I was taking kelp capsules for a while, but then got to thinking that I did not know where the kelp was coming from. If it is from almost anywhere in the Pacific then I would worry about putting more radiation in my body by taking irradiated kelp.

    • Yeah, anything from the Pacific is so full of radiation it is either dead or lethal.I had been taking Krill Oil and have been reading about massive die-offs of Krill on our west coast. I would be concerned with the sources of fish oil as well. Omega – 3s are important but not if so contaminated as to be more harmful than no supplementation at all.

  6. I’m not certain I understand the dosages you list. When you write 1 / 2, do you mean 1 to 2 tablets, or do you mean 0.5 tablet?
    Otherwise, a well written article.

    • Bernie, Good catch – I can see where that may be confusing. I am adding this update as follows:

      Update: This reference is referring to the 130 mg tablet. 1/2 = 65 mg.

  7. And remember folks, the half-life of Iodine-131 is 8 days. No point in taking iodine pills if it’s over a week after the event.


    If you’re really worried about radiation exposure, don’t fly in airplanes. Your risk of exposure is much greater than anything that might be coming out of your neighborhood nuclear generating station (your coal-fired generating station is another story), and certainly anything in the air from Japan.

  8. And remember folks, the half-life of Iodine-131 is 8 days. No point in taking iodine pills if it’s over a week after the event.

    Just to quibble a little, it’s not as if the radiation level falls to zero after 8 days, so there’s still some point in taking iodine pills a week later. Depending upon the initial level of contamination, several half-lives may be necessary for the risk to fall to an acceptable level to where blocking therapy is no longer called for.

  9. The NukAlert is an insensitive detector that doesn’t begin to issue alerts until exposure is at 100 counts a minute, which used to be the “bug out level” until the Goverment changed it’s recomended “safe doseage” . Best detector at reasonable cost appears to be “Inspector Plus” . Before you ask ,no I don’t work for any dector company,but I have done some research on detectors and I did buy a Nukalert before I knew better . Save your money as the vendor I bought from refused to refund my money.

  10. So what do you do if you’ve already had your thyroid removed completely and your para-thyroid? These pills I take every day just seem worthless. One doctor I go to syas I should be taking double the dose. My regular doctor says I’m within the lines for the dose I’m taking. I feel so much better when I double but then run out of pills.

  11. Kind of disconcerting – I had Hashimoto’s, and no longer have a thyroid. But this info is good to know for my family.

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