How to Use Potassium Iodide for Radiation Protection

Potassium iodide is a white crystalline powder.
Potassium iodide is a white crystalline powder.

If the statements coming from North Korea at present are to be believed, there’s a possibility they’ll be launching a nuclear attack on us some time after Wednesday 10 April.  Whether this happens or not, it is well to be prepared for such a situation.

Defending against a nuclear attack is both easy and difficult, and for sure you need to understand that a nuclear bomb detonation is not an Armageddon like event that will destroy all life, everywhere, for hundreds of miles around.  Quite the opposite of what popular media would wish you to believe, a nuclear blast is a surprisingly limited impact event and very survivable.

So, if you survive the immediate gamma and neutron radiation, heat and overpressure wave (see our article on Radiation and Fallout Risks for a detailed explanation of these issues) what should you do next?

What you do next really depends on if the blast was a ground or an air burst.  If the former, you’ll be exposed to an appalling mess of radioactive fallout for some time and everything around you will have the fallout on it.  That’s really nasty and probably your only practical option is to quickly evacuate the area, getting some tens or ideally hundreds of miles upwind of the event.

An air burst creates much less fallout, and that which is created is spread thinly over a much greater region.

There is one easy and inexpensive thing you can do as a protective or prophylactic measure, and that is to take Potassium Iodide tablets.  These act to block your thyroid gland from absorbing radioactive iodine from the fallout.  They do not protect you against any of the dozens of other forms of radioactivity, but the iodine in particular can be a concern because it potentially will injure the thyroid due to being absorbed and concentrated in the thyroid for a period of time.

Furthermore, the inexpensive tablets do little other harm, so on the basis of ‘Better Safe than Sorry’ it is usually considered prudent to go on a course of Potassium Iodide tablets if you are exposed to radioactive contamination of a type that might include radioactive iodine.

This article tells you what you need to know.

The Difference Between Iodine, Iodide, and Iodate

Iodine is the name of the element that we are talking about.  Its chemical symbol is the letter I.

Iodide is used to refer to a form of Iodine that has reacted with another material to create a chemical compound.  The most common form we see this in, for our purposes, is in a ‘salt’ (the chemical term ‘salt’ refers to a type of compound, rather than specifically to Sodium Chloride or common table salt as we know it) called Potassium Iodide – chemical formula KI.

Iodate is another type of chemical including Iodine, and is commonly found in another type of ‘salt’, Potassium Iodate – chemical formula KIO3.  Potassium Iodate is usually the type of Iodine that is added to iodized (table) salt.

There are other materials that also include iodine, and you might sometimes see reference to Potassium Iodite.  Our understanding (Hello, Undergrad Chemistry classes – remember us, all those decades ago? 🙂 ) is that Potassium Iodite is an unstable non-natural compound and not likely to be found in the real world, and if you see a product being sold as Potassium Iodite it is probably a misspelling of Potassium Iodide.

Our suggestion – if a supplier can’t even spell the name of the product they are selling correctly, best to steer well clear of them!

Pure iodine is difficult to take and toxic in other than very small quantities, so when people are choosing to take iodine supplements, they will usually choose either Potassium Iodide or Potassium Iodate.

Which is Better – Potassium Iodide or Potassium Iodate?  Tablets or Liquid?

You’ll see some websites making extravagant claims about the relative merits of either Potassium Iodide or Potassium Iodate.  Ignore these comments.  In reality, there’s very little difference between the various forms of iodine you’ll come across.  But, while there are only small differences, there are indeed better and not so good forms, so let’s understand which are (slightly) better choices than others.

The most authoritative source we could find – and trust – is a World Health Organization report (linked in the reference section below) which on page 17 says :

Stable iodine can be used either as potassium iodide (KI) or potassium iodate (KIO3).  KI is the preferred alternative, since KIO3 has the disadvantage of being a stronger intestinal irritant.

There is no decisive difference in shelf life between KIO3 and KI.

So there’s your answer.  Both are okay, but Potassium Iodide is slightly to be preferred over Potassium Iodate, if you find yourself with the luxury of being able to choose between them.  (And note, below, that the dosage levels are different.)

You’ll also notice different forms of packaging for the chemicals.  Again, let’s use the WHO report as our source, with their comment (also on page 17 of their report) again giving clear guidance :

Stable iodine can be given in either doubly scored tablet or liquid form.  Tablets have the advantage of easy storage and distribution, including predistribution.  Also, stable iodine is likely to cause less gastrointestinal irritation if administered in tablet form.  Tablets can be crushed and mixed with fruit juice, jam, milk or similar substance.

Tablets should be stored protected from air, heat, light and moisture.  Age-dependent dosage and contraindications should be on the labeling.

Tablets packed in a hermetic alufoil and kept in a dry and cool place preserve fully their iodine content for 5 years.

So – tablets are better than liquids.

Officially Approved vs Unofficial Tablets

Potassium Iodide tablets do not require a prescription.  You can buy them in many different places, even (of course!) on Amazon.

The FDA has approved three brands of Potassium Iodide tablets – Iosat, ThyroSafe, and ThyroShield .  These are the only brands of tablets which can claim to be FDA approved, but many other brands of tablets are also available.

If you buy an FDA approved brand, you know for sure that you actually have the iodine ingredients as promised, and in the quantity claimed.  If you buy any of the other brands of non-FDA approved products, unless you have the ability to test and analyze the tablets, you have no way of knowing what ingredients may – or may not – be present.

Other brands are probably exactly as they claim to be.  But do you really want to risk your future health based on a hope that the generic product truly is what it claims to be, when an official product is only a few dollars more?  No, we didn’t think so.  🙂

Risk Factors

Stated simply, the older you are, the less you have to worry about any type of radiation exposure, because you’ll probably be dead of natural causes before the radiation has an effect.  Indeed, the World Health Organization does not recommend that adults over the age of 40 should take Potassium Iodide at all, unless it is certain they were exposed to a very high level of radioactive iodine (ie 500 times greater than the level that would require taking the tablets in young children, and 50 times greater than the level required by adults under the age of 40).

On the other hand, the younger you are, then clearly the greater the risk you have and the more years hopefully ahead of you.

So if you have a shortage of iodine, give it first to the younger people in your group, and last to the older members.


You need to urgently start taking iodine tablets as soon as possible after a radiation exposure event.  There is no value or reason to take them before a radiation event (ie wait until the bomb goes off nearby).

You should take one tablet each day during the period of radiation exposure, stopping as soon as radiation levels have declined below a level of concern (most likely meaning you’ve evacuated the area).

Recommended dosages are equivalent to 100 mg of actual iodine, which requires 130 mg of Potassium Iodide or 170 mg of Potassium Iodate.

Age Raw Iodine mg Potassium Iodide mg Potassium Iodate mg Liquid* ml
Birth to 1 month 13 16 21 0.3
1 month – 3 years 25 33 43 0.5
3 – 12 years* 50 65 85 1
Over 12 yrs* 100 130 170 2

Note 1 :  This assumes a typical strength of liquid solution.  There is no guarantee as to what strength a liquid solution may be, so check with the guidelines given by the provider – and this uncertainty is another reason to prefer tablets over liquids.

*  Note 2 :  The FDA and WHO disagree about when children should be switched to adult dosage levels.  The FDA says wait until children are over 150lb or over 18.


You should keep a stock of Potassium Iodide tablets in a cool dry place as part of your prepping supplies.

In the event of a nearby radioactive release (either from a nuclear weapon, a ‘dirty bomb’, or a power plant accident) those of you 40 and under in your group should immediately start taking daily iodine tablets until you have evacuated the area.


Here is an excellent but somewhat technical document from WHO.

Here is the US CDC sheet on Potassium Iodide.

Here is the US FDA fact sheet on Potassium Iodide and here is their more detailed PDF.

One Reply to “How to Use Potassium Iodide for Radiation Protection”

  1. lucifersbobsled

    Many thanks to David for putting this out there! (As a former nuclear industry worker, I went shopping for Potassium Iodide when Fukushima let go. Up here in Canukistan, all I got was abuse from local drug stores when I asked for it- far as I know, it is not available here). I finally found a source at It cleared the border, labelled as a ‘dietary suppliment’- haw!)
    David Spero is correct- when he states that this is not recommended for adults- but consider that this is issued to troops who are fighting in a nuclear war zone. The tabs that I got from sportsmansguide are the 32.5 mg which are recommended for children- they are intended for my grandson.
    Back in the ‘eighties, when Chernobyl went up- and the local authorities finally admitted that they had a ‘little problem’, (after Scandinavia detected the fallout)- the Russians gave chocolate bars, laced with Bentonite Clay- to the children around Pripyat. (Bentonite Clay- also called Montmorillonite- removes radioactivity from the body by a process called ‘Ionic transfer’ Heavy metals emit positive ions- Bentonite Clays are negative ions.
    (I asked Arnie Gunderson- over at Fairewinds- about this: Arnie’s response: “I am an engineer- not a doctor- talk to this guy about this. He has written a book about it.” (Thanks, Arnie)! has food-grade Bentonite Clays and blends-check them out. (They recommend a spoon full in a glass of water or fruit juice, as body flush- Native Americans have known about this for generations.)

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