Iodine prophylaxis: everything you need to know



What is the idea of iodine prophylaxis?


Radioactive iodine is a short-lived isotope present in radioactive releases under accidents at NPP reactors. It can be easily spread with wind and remains hazardous for a month at least, gest accumulated in the thyroid gland and irradiates it with beta particles and gamma rays.

The thyroid gland uses iodine to produce metabolically active hormones, absorbing both stable and radioactive iodine. Radioactive iodine enters the body by inhalation (as part of aerosols) or ingestion (along with food) after an accident involving the release of radioactive aerosols.

Therefore, the goal of iodine prophylaxis is to prevent the iodine radioactive isotope from entering the thyroid gland by saturating it with stable iodine.

When is it necessary to carry out iodine prophylaxis?



Potassium iodide is efficient only in the event of an accident at a nuclear power plant with a confirmed release of radioactive substances with the presence of radioactive iodine, provided that the radioactive cloud is guaranteed to be in your area. Taking potassium iodide is justified only under such predicted doses of thyroid gland exposure due to ingestion of radioactive iodine, the risk of which exceeds the risk of consequences of thyroid blockade with potassium iodide.

According to research, when taking potassium iodide immediately after receiving radioactive iodine, the radiation dose of the thyroid gland is reduced by 20 times, in an hour after the intake: at least 10 times, 2 hours: 4 times, 3 hours: just twice, after 15 hours: not more than 20%.

Normally, just one stable iodine dose is sufficient. However, re-administration may be required in case of prolonged (more than 24 hours) or repeated exposure, if it is impossible to prevent the intake of contaminated food.

What daily iodine dose is considered normal?


Depending on age, the daily iodine requirement is from 90 to 300 mcg.

For adult women, the daily iodine intake shall be 150-300 mcg, for men: up to 300 mcg.

Iodine intake rates for children:

0-6 years: 90 mcg;

6-12 years: 120 mcg.

Most Ukrainians consume just 40-80 mcg of iodine per day. The lowest iodine consumption is in Western Ukraine and Chernihiv region.

WHO experts consider a safe dose of iodine of 1,000 mcg (1 mg) per day. Throughout the life span, a person consumes about 3-5 g of iodine, which is about one teaspoon.

When potassium iodide shall be taken?

The optimum effect of iodine prophylaxis is achieved by premature (preventive) administration of iodine at 6 or fewer hours before intake of radioactive iodine. In addition, the high efficiency of iodine prophylaxis (90-100%) is maintained when taking iodine preparations directly before or within 30 minutes from the beginning of inhalation of radioactive iodine aerosols. The protective effect starts 5 minutes after taking a pill on an empty stomach and 30 minutes after taking a pill on a full stomach.

In 2 hours after the intake of radioactive iodine into the body, the effectiveness of iodine prophylaxis decreases sharply. The onset of the blockade 24 hours after the start of radioactive iodine aerosols inhalation will do more harm than benefit, as it may prolong the biological half-life of radioactive iodine that has already accumulated in the thyroid gland.

Under skin application of iodine solution, the protective effect starts with a delay depending on the skin properties (thickness of dead epithelium, greasiness, number of pores). Children have skin thinner, non-greasy, with lots of living pores, so the absorption of iodine through the skin will be the fastest.

Determined dosage of the drug (see Dosage Table) is sufficient for about 2 days, then, with continued intake of radioactive iodine, it is possible to repeat the medication.

Alcohol consumption during iodine prophylaxis is strictly prohibited.

What is the best to take iodine?

The recommended dose of potassium iodide is 1000 times higher than the body’s daily need for iodine. If the preparation of potassium iodide is taken in advance, it is recommended to take it after meals. In case of the urgency to introduce stable iodine into a body, it is possible to accept the drug on an empty stomach.

To use potassium iodide pills for children, the pills can be crushed and mixed with low-fat liquids such as milk, chocolate milk, orange juice, sweet carbonated water, etc.

Raspberry syrup improves the salty taste of potassium iodide the best.

Where potassium iodide can be received?


The public protection plans define the conditions and procedures for providing potassium iodide drugs, which should ensure the urgent availability of these drugs in the area of ​​iodine prophylaxis (currently these are only NPP observation areas). The procedures are established taking into account the peculiarities of the infrastructure of the territory. Potassium iodide providing procedures may include: free distribution of potassium iodide preparations by special teams; delivery to houses, apartments; getting drugs for free in pharmacies, etc. Such procedures are calculated and specified as soon as possible in response to a nuclear accident.

The number and location of potassium iodide preparations distribution points are determined by local executive bodies and local self-government authorities based on the proposals of territorial administrations (departments) for health care, education, housing, and communal services.

The issue of iodine prophylaxis outside the NPP observation areas remains open. Although, for example, under the ChNPP accident in 1986, the need for iodine prevention measures arose, at least in the area of ​​500 km around the Chornobyl NPP.

Who makes a decision on iodine prophylaxis?


The decision on iodine prophylaxis is made by local executive bodies based on the radiation situation prognosis and on information provided to local executive bodies by operating NPP representatives, the Ministry of Health of Ukraine, and the SES of Ukraine.

The direction of radioactive substances clouds released from nuclear power plants during an accident, and the nature of their deposition are directly related to wind speed and direction, humidity, temperature, and precipitation. Thus, the distribution of radioactive particles can remain relatively local or spread over long distances depending on weather conditions. These processes are monitored to identify specific areas for countermeasures.

Who is responsible for conducting iodine prophylaxis?

Notification and informing the public on the start of iodine prophylaxis is carried out by local executive bodies immediately after the decision on the need for iodine prophylaxis.

The public is informed on how to behave in the event of a radiation accident, where to get, when, and how potassium iodide shall be taken. The public is informed through all available mass media. Under providing information the public is warned about the need to avoid overdose and poisoning with iodine preparations.

What happens if you do not take iodine during an NPP accident with a release of radioactive iodine?

Iodine is rapidly absorbed into the blood by inhalation or ingestion and after distribution in the extracellular space, it is transported and concentrated in the thyroid gland. The absorption rate by the gland for healthy people is from 10 to 40% of the total intake of iodine in the body, and about half of this amount enters the gland within 3-6.5 hours. If the thyroid gland absorbs radioactive iodine, it leads to radiation exposure of the gland tissue, which can lead to its slow destruction, hypothyroidism, or significantly increase the risk of thyroid cancer in the long run.

Since our area constantly experiences iodine deficit, we may be affected by radioactive iodine to the higher extent.

What should people with no thyroid gland do?

Iodine is not a protection against radiation in itself, it is only a protection for a healthy thyroid gland. Individuals with a thyroidectomy experience, which implies complete removal of the thyroid gland, and taking drugs to correct hypothyroidism, do not need to take iodine.

Who does not need to take iodine?

Stable iodine preparations should be used with caution by persons with the following disorders, as they have relative contraindications to the use of stable iodine preparations:

–     presence of thyroid disease (past and present);

–     hypersensitivity to iodine;

–     herpetiform dermatitis;

–     hypocomplementemic vasculitis;

–     congenital myotonia.

–     availability (including in the anamnesis) of thyroid disease,       in particular, hyperthyroidism of various natures;

–     furunculosis;

–     toxic adenoma;

–     hemorrhagic diathesis;

–     urticaria

–     pulmonary tuberculosis;

–     nephritis, nephrosis;

–     pyoderma.

If you are not sure if you should take potassium iodide, please talk to your family doctor.

Will Iodine-vitamin supplements Help?


Such drugs contain only a daily iodine dose, normally it is 150 mcg. For the radioprotective effect it would be necessary for an adult to take 850 such pills at a time, at a dosage of 125 mcg in the drug supplement: 1000 pills at a time, 1250 pills at a dosage of 100 mcg. Therefore, “iodine” pills available in pharmacies contain a meager amount of potassium iodide and are not useful for urgent protection against radiation. At the same time, by taking such drugs on a regular basis for a long time before the intake of radioactive iodine, an individual just covers iodine deficiency and reduces the risk of absorption of radioactive iodine.

In the absence of pills of potassium iodide, is it possible to take an alcoholic tincture of iodine, Lugol’s, or Betadine solution?

!! As iodine prophylaxis, alcohol tincture of iodine and Lugol’s solution are prescribed ONLY for SKIN use. Ingestion of tincture of iodine, Betadine, or Lugol’s solution can cause severe mucosal burns and poisoning. Numerous studies have confirmed the effectiveness of the cutaneous application of iodine alcohol tincture and Lugol’s solution in the recommended dosage at the level of a single dose of potassium iodide orally (see the dosage table).

Alcoholic iodine solution, as well as Lugol’s glycerol solution, contains molecular iodine in addition to potassium iodide, which does not enter the bloodstream immediately and when ingested can cause damage and burns to gastrointestinal tissues, poisoning due to the iodine toxicity as halogen. These drugs should be applied to the skin only. To be applied to the skin of the forearm or leg (to be repeated in two days if a risk of radioactive iodine intake remains).

Attention: allergy is possible when applied to the skin, be sure to check the reaction before applying a drop of the drug on the inside of the wrist.

What shall be done if iodine is not available and it is not possible to obtain it, and there is a risk of radioactive iodine intake?

If there are no iodine-containing drugs or the risks are too high, please follow the strictest aerosol hygiene: anti-aerosol filters class not lower than FFP3 for respiratory organs, protect exposed skin with any polymeric (non-porous) materials. Do not consume contaminated food or water to prevent oral exposure to radioactive iodine.

In the last case, if you can not find iodine, you can consume food rich in stable iodine (seaweed, cod and liver, shrimps, tuna, prunes, feijoa, persimmons, walnuts) or goitrogen-rich food that blocks the iodine intake in the thyroid gland in general (horseradish, mustard, soy, broccoli, spinach prevent the iodine absorption, thus suppressing thyroid gland function).

Are any side effects of thyroid gland blockade possible?

When taking a large dose of stable iodine there is a possibility of side effects, which vary widely depending on the iodine amount in the food ration and the availability of thyroid disease (the number of elderly patients is much higher compared to infants and adolescents).

Side effects of stable iodine include sialodenitis, gastrointestinal disorders, allergic reactions, minor rashes, iodine-induced thyrotoxicosis, transient hypothyroidism, and goiter, and a low risk of death cases.

Why is it not recommended to block the thyroid gland for people over 40-45 years?


The risk of radioinduced thyroid cancer for adults aged over 40 years is quite low, so adults over 40-45 should take potassium iodide only in case of a predicted high internal dose of thyroid radiation (>5 Gy). Iodine prophylaxis for people aged 40-45 years can lead to further hypothyroidism, the main manifestations of which are general weakness, drowsiness, fatigue, slow speech and thinking, decreased appetite, swelling, low body temperature; changes in voice, and hearing loss due to swelling of the larynx, tongue and middle ear in severe cases, from the cardiovascular side: decreased cardiac output, bradycardia, increased blood pressure; as for the lungs, it is hypoventilation and pleural effusion; as for the gastrointestinal tract, it is nausea, constipation, bloating; the skin problems are hair loss, dryness, and fragility, often yellowing of the skin; the peripheral nervous system suffers from the decreased tendon reflexes.

How many times per day do you need to take potassium iodide?

As a rule, stable iodine should be taken only once. A single dose of potassium iodide pills in appropriate dosages provides a complete blockade of the thyroid gland during the day. For some public groups (please see Dosage Table), repeated or multiples doses of potassium iodide are allowed in case of threat of repeated, prolonged, or multiple intakes of iodine radioisotopes by inhalation or with milk or other food.


Dosage according to the public groups:

Public groups, age



Intake duration

Consequences/negative effects

Babies from birth up to 1 month

16 mg of potassium iodide in pills

Certain amount of the preparation should be administered to both breastfed and formula-fed infants.


Single time

For newborns, prolonged blockade of thyroid function increases the risk of reduced adaptive capacity in the transition to extrauterine life, and the risk of mental retardation. Changes can be irreversible. Only a single dose of blocking doses of the protective drug is allowed.

Children (from 1 month up to 3 years)


32 mg of potassium iodide pills INTERNALLY or EXTERNALLY

10 drops of 5% iodine solution or 5 drops of Lugol’s solution on the forearm skin or shin to be applied once a day



For children, due to higher functional activity and smaller size of the thyroid gland, the accumulation of radioactive iodine in the gland occurs in large quantities, faster, and higher absorbed doses are formed. Maximum absorbed doses per activity unit of radioactive iodine are formed approximately 10 times higher than in adults.


Repeated intake is allowed (after 24 hours) (skin application: in two days, if there is a risk of radioactive iodine intake)



For children aged from 1 month up to 3 years, multiple doses of thyroid-blocking doses of the protective preparation increase the risk of temporary delay in psychomotoric development, metabolic disorders, and physical development.

Children (from 3 up to 12 years)

62.5 mg pills of potassium iodide INTERNALLY or EXTERNALLY 20-22 drops of 5% iodine solution or 10 drops of Lugol’s solution to be applied to the skin of the forearm or a leg once a day


As the child’s age increases, the levels of accumulation of radioactive iodine in the thyroid gland decrease, and up to 14 years correspond to the levels of its accumulation for adults.


Repeated and multiple doses are allowed (once per day for 5 days)


For 3-14-year-old children and adolescents, prolonged blockage of the thyroid gland function can lead to a temporary delay in growth and development, and metabolism, which is restored with the restoration of thyroid function. Multiple usage of a protective product is allowed.



Adolescents (over 12 up to 18 years)

125 mg pills of potassium iodide INTERNALLY or EXTERNALLY

40-44 drops of 5% iodine solution or 20 drops of Lugol’s solution to be applied on the forearm or shin skin once per day

Repeated and multiple doses are allowed (once per day for 5 days)


Adults (up to 40 years)

125 mg pills of potassium iodide INTERNALLY or EXTERNALLY

40-44 drops of 5% iodine solution or 20 drops of Lugol’s solution to be applied on the forearm or shin skin once per day


Individuals who may receive high doses (from 5 Gy) from exposure to radioactive iodine (e.g., emergency workers involved in rescue or response operations) are likely to benefit from the blockade, regardless of age, and should be preferred.


Repeated and multiple doses are allowed (once per day for 5 days)


About 30% of the total intake of radioactive iodine accumulates in the thyroid gland of an average adult.


Pregnant women

125 mg pills of potassium iodide INTERNALLY or EXTERNALLY

40-44 drops of 5% iodine solution or 20 drops of Lugol’s solution to be applied on the forearm or shin skin once per day


Pregnant women, due to increased thyroid function, have levels of accumulation and formation of absorbed doses in the thyroid gland approximately 1.5 times higher than average adults. During pregnancy, the maximum absorbed doses in the fetus are formed before birth.


Single time


Breastfeeding mothers

125 mg pills of potassium iodide INTERNALLY or EXTERNALLY

40-44 drops of 5% iodine solution or 20 drops of Lugol’s solution to be applied on the forearm or shin skin once per day


Lactating women have up to 30% of the radioactive iodine in the breast milk during the day. Lactation is one of the most important ways of removing radioactive iodine from the mother’s body and is an additional hazard to the child.



Single time


Adults (over 40 years)

125 mg of potassium iodide pills INTERNALLY are recommended only under radiation levels that may cause deterministic effects? Which are 5 Gy of the expected dose to the thyroid gland



Individuals over 40 and people with pre-existing thyroid disease are more likely to suffer from thyroid blockage than from radioactive iodine: the risk of radioinduced thyroid cancer for adults over 40 is low.




Single time

(should not be re-exposed to iodine blockade due to the risk of side effects)


For adults over 45, prolonged thyroid dysfunction for men and women increases the risk of functional disorders of organs and systems regulated by thyroid hormones (cardiovascular, nervous, immune, etc.). The risk of thyroid disease, including malignant neoplasms, is increasing, and diseases of a number of organs and systems functionally related to thyroid activity may be complicated. Diseases are progressive in nature and difficult to treat. Older women are at high risk for thyroid hormone deficiency. It is permissible to take a single protective drug only at the risk of inhalation and formation of high doses of thyroid radiation (5 Gy)


  1. Order of the Ministry of Health of Ukraine dated 09 March 2021 No. 408, registered in the Ministry of Justice of Ukraine on 16 April 2021 No. 526/36148 “On Approval of the Procedure on Iodine Prophylaxis in Case of a Radiological Emergency”.
  2. World Health Organization. (‎2017) ‎. Iodine Thyroid Blocking: Guidelines for Use in Planning for and Responding to Radiological and Nuclear Emergencies. World Health Organization.
  3. Guidance Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies U.S. Department of Health and Human Services Food and Drug Administration Center for Drug Evaluation and Research (CDER) December 2001 Procedural
  4. SNRIU Order dated 08 November 2011 No. 154, registered in the Ministry of Justice of Ukraine on 25 November 2011, No.1353/20091 “On Approval of the Procedure for Implementing Iodine Prophylaxis Measures in Case of a Radiological Emergency”.
  5. Effectiveness of Skin Absorption of Tincture of I in Blocking Radioiodine from The Human Thyroid Gland, Kenneth L. Miller, Patricia E. Coen, William J. White, W. Jeffrey Hurst, Bryan E. Achey and C. Max Lang College of Medicine, The Pennsylvania State University, The Milton S. Hershey Medical Center, Hershey, PA 17033 (Received 13 August 1988; accepted 15 December 1988)
  6. PL Detail-Document, Compounding KI for Radiation Exposure. Pharmacist’s Letter/Prescriber’s Letter. March 2011.
  7. Frequently Asked Questions on Potassium Iodide (KI), US Food and Drug Administration (FDA)

LIFEHACK (A chemist’s blog (Sergey Besarab ~ Siarhei Besarab)

Iodine tincture can cause serious injuries under peroral intake, the risk of an accident at an NPP is high, and there is no potassium iodide. What to do in this case?

If you have a bottle of 5% alcohol iodine tincture and have access to a pharmacy where you can get injectable 30% sodium thiosulfate in ampoules of 10 ml (Sodium thiosulfate solution for injections 300mg/ml in ampoules of 5 ml, 10 pcs, Darnytsia production), using these two components you can make an effective radio-protective cocktail, which, among other issues, is quite convenient for dosing.

10 ml of pharmacy iodine tincture (standard vial) contains 0.2 g of potassium iodide we need and 0.5 g of elemental iodine, which is harmful to the gastrointestinal mucosa. It can be neutralized with sodium thiosulfate. An ampoule of 5 ml of 30% solution contains approximately 1.5 g of sodium thiosulfate. This ampoule is sufficient for one vial of 5% alcohol tincture. Thiosulfate is safe in general and is used as an antidote for halogen poisoning.

In the simplest application, you can simply drip thiosulfate solution in iodine until the solution is completely discolored until the brown color disappears (and a couple of drops on top, “for being confident”).

Approximately 2 ml of sodium thiosulfate should be added to 10 ml of iodine tincture. As a result, we will obtain 12 ml of liquid containing 0.8 g of a mixture of iodides. It is completely safe. Since the solution is diluted and aqueous, a drop size is 0.05 ml. One ml of our solution (20 drops) contains approximately 67 mg of iodide (3.3 mg in one drop). Therefore, to receive an adult radioprotective dose of 125 mg of iodine you need to drink 38 drops, infants from birth up to 1 month shall take 5 drops, children (from 1 month up to 3 years) 10 drops, children (from 3 up to 12 years) 19 drops, adolescents (over 12 up to 18 years) 38 drops.

You need to buy the components and make the right solution in advance. The prepared preparation can be stored for a long time (conservation effect of alcohol). Calculate the number of drops for each family member and sign a container with the solution. Do not postpone it until the last moment.

The material was prepared by SSTC NRS experts