Lugol’s Iodine: Not Created for Daily Supplementation
Progress is impossible without change, and those who cannot change their minds cannot change anything. – George Bernard Shaw
What Is Lugol’s Iodine?
Lugol’s iodine is a solution of iodine and potassium iodide in water. The classic 5% strength has 5 g of iodine and 10 g of potassium iodide per 100 mL.1 That works out to about 126 mg of iodine in every mL, and about 40% of that iodine is free molecular iodine. In the United States, Strong Iodine Solution USP (Lugol’s Solution) is a prescription drug.1
Iodine barely dissolves in water on its own, only about 0.03 g per 100 mL.2 Adding potassium iodide is what let Lugol dissolve far more, so the 5% solution holds over 150 times as much iodine as plain water could.
Who Created Lugol’s Iodine, and Why?
Iodine was discovered in 1811, when the chemist Courtois noticed a violet vapor rising from burning seaweed ash. Doctors were giving it by mouth within a few years. In 1813 the Swiss physician Coindet reasoned that seaweed helped goiter because of its iodine, and he treated his patients with iodine itself.3
The French physician Jean Lugol first made his solution in 1829 as an iodine medicine for his patients at the Saint-Louis hospital in Paris. He is remembered as a “French pioneer of iodine therapy”, and his solution is still registered in the French Codex and in most other pharmacopoeias.4 Iodine solutions later became widely used as antiseptics for wounds.5
So Lugol’s iodine was made as a medicine for a course of treatment. It was never made as a daily supplement.
What Is Lugol’s Solution Used For Today?
Lugol’s iodine has many uses in medical science as a stain, because it colors different tissues, and tissues with specific properties, in different ways. Doctors spray it inside the gut during endoscopy to highlight the lining.6
Lugol’s iodine has also long been used to supply iodine, and its drug label still lists the prevention of simple goiter.1 Iodine solutions can also be used to treat water in an emergency. Our Iodine for Preppers guide gives the official method.
Is Lugol’s Iodine Safe to Drink?
Since it contains free iodine, Lugol’s solution at 2% or 5% concentration without dilution is irritating and destructive to mucosa, such as the lining of the esophagus and stomach. The free (molecular) iodine is what makes it irritating to the mouth, throat and gut. Even sprayed onto the stomach lining during endoscopy, Lugol’s iodine has caused acute damage to it.6 The drug label warns that swallowing large quantities “may cause abdominal pain, nausea, vomiting and diarrhea.”1
The form matters too. The World Health Organization says stable iodine is likely to cause less stomach and gut irritation as a tablet, and that its shelf life “is much more limited if stable iodine is in powder form or an aqueous solution.”7
“Stable iodine is likely to cause less gastrointestinal irritation if administered in tablet form.” – World Health Organization
Lugol’s vs Potassium Iodide: What’s the Difference?
Lugol’s iodine contains two forms of iodine: free molecular iodine and iodide (from potassium iodide). Potassium iodide (KI) provides iodide only. Here is how the three compare:
| Forms of iodine | Share of the iodine as molecular iodine | Iodine per unit | How it is sold in the US | |
|---|---|---|---|---|
| Lugol’s iodine5% | Molecular iodine + potassium iodide | About 40% | About 126 mg per mL | Prescription solution1 |
| Potassium iodide tablet130 mg | Potassium iodide | 0% | 100 mg per tablet | FDA-approved, without a prescription, for thyroid blocking8 |
| Zen Haus Iodine tablet | Molecular iodine + potassium iodide | 25% | 12.5 mg per tablet | Dietary supplement |
For thyroid blocking, the amount of iodine is what counts. The WHO says potassium iodide is the agent most commonly used, and that other forms “are equally valid, provided that the dosage is adapted to contain the same amount of iodine.”7 What sets potassium iodide tablets apart is the measured dose and the absence of the free iodine that makes concentrated Lugol’s harsh. That fits what we found in our Why KI? series: potassium iodide is a gentler, measured way to take iodine than a free-iodine solution.
In Why KI? Part 4 we look at how molecular iodine is converted to iodide in the stomach and compare the elemental iodine in Lugol’s and KI tablets mg for mg. For how nascent iodine compares, see nascent iodine vs Lugol’s.
Lugol’s Iodine and Chernobyl: What Poland Really Gave
After the Chernobyl accident in 1986, the Polish radiation expert Zbigniew Jaworowski proposed Lugol’s liquid (płyn Lugola in Polish) for children. In his words, it was “a solution of stable iodine compounds, logistically more handy than potassium iodide tablets.”9
What Poland’s Minister of Health actually ordered the central pharmacy to prepare, on April 29, 1986, was a potassium iodide solution, sent to the 11 provinces most affected.10 According to the US FDA, about 10.5 million children and 7 million adults in Poland received at least one dose of potassium iodide. The FDA describes the side effects as “generally mild and not clinically significant.”11
Potassium Iodide for Radiation Emergencies Today
The WHO explains it simply: “The thyroid gland can be protected from radioactive iodine by saturating it with stable (non-radioactive) iodine.” This is done with potassium iodide tablets.12 The FDA calls the effectiveness of KI as a specific blocker of thyroid radioiodine uptake “well established,”8 and it says the Polish experience supports KI as a safe and effective way to protect the thyroid when exposure can’t be avoided.11
Timing is what matters. The WHO says potassium iodide works best when taken less than 24 hours before, and up to 2 hours after, exposure starts. Taken more than 24 hours after exposure, it offers no protection. KI protects only the thyroid, and only from radioactive iodine. It works alongside sheltering, evacuation and avoiding contaminated food and water, and it should be taken only when public health officials say to take it.12
In the United States, the only products that may be marketed for thyroid blocking are FDA-approved potassium iodide products.8 Lugol’s isn’t one of them, and neither is our tablet. The adult dose is 130 mg of potassium iodide, which is 100 mg of iodine.7 That is about 8 of our tablets, which is why it has to be a purpose-made KI tablet. Keep FDA-approved KI in your kit. Our Iodine for Preppers guide has the doses by age, and we discuss the wider picture in Radiation Health Risks – Part 3: Mitigating The Risk.
Why Our Tablet Is Iodide First
Each Zen Haus Iodine tablet has 12.5 mg of iodine from 3 mg of molecular iodine and 12.7 mg of potassium iodide: 75% iodide and 25% molecular iodine. In 5% Lugol’s, about 40% of the iodine is molecular iodine.
Small amounts of molecular iodine are a different story from a concentrated solution. Molecular iodine enters tissues through its own facilitated diffusion route, separate from the transporter that carries iodide.13 In a 6-month trial of 1.5 to 6 mg of molecular iodine a day, all doses had an acceptable safety profile.14 Our tablet has 3 mg.
Seaweeds contain iodide plus other, non-iodide forms of iodine. We compare their balance with supplements in Iodine and Iodides in Seaweeds and Supplements. Each tablet also includes selenium (40 mcg, as L-selenomethionine) and riboflavin (1.3 mg).
Lugol’s iodine was created as a medicine. Health authorities protect the thyroid with potassium iodide tablets. For daily intake, we chose a measured tablet that is iodide first, with less molecular iodine than Lugol’s.
FAQ
What is Lugol’s iodine?
Lugol’s iodine is a solution of potassium iodide and molecular iodine in water, named after the French physician Jean Lugol, who first made it in 1829. The classic 5% strength has 5 g of iodine and 10 g of potassium iodide per 100 mL.
What is Lugol’s iodine used for?
It is used in medicine as a stain to highlight specific tissues, for example during endoscopy. Iodine solutions are also used as antiseptics and, in emergencies, to treat water. Lugol first made it in 1829 as an iodine medicine for his patients, not as a daily supplement.
Is Lugol’s iodine the same as potassium iodide?
No. Lugol’s iodine is molecular iodine plus potassium iodide in water, and about 40% of its iodine is free molecular iodine. Potassium iodide provides iodide only. Our tablet is 75% iodide and 25% molecular iodine.
Is Lugol’s iodine safe to drink?
Undiluted 2% or 5% Lugol’s iodine is irritating and destructive to the lining of the mouth, throat and gut because of its free iodine. The World Health Organization notes that stable iodine is likely to cause less gastrointestinal irritation in tablet form.
Can Lugol’s iodine be used for radiation protection?
Health authorities use potassium iodide tablets, taken only when public health officials say to. In the United States, only FDA-approved potassium iodide products may be marketed for thyroid blocking. Our Iodine for Preppers guide has the doses by age.
Who invented Lugol’s iodine?
The French physician Jean Lugol, a pioneer of iodine therapy at the Saint-Louis hospital in Paris. He first made his solution in 1829 as an iodine medicine for his patients.
Is Lugol’s iodine radioactive?
No. Lugol’s iodine contains stable, non-radioactive iodine. Stable iodine is the kind the World Health Organization says can saturate the thyroid so that radioactive iodine is not taken up.
Does Lugol’s iodine expire?
The World Health Organization notes that the shelf life of stable iodine is much more limited in powder form or as an aqueous solution than as tablets in hermetic packaging. Check the expiry date on the label.
