The iodine tablet protects the thyroid gland

A serious nuclear power plant accident may release radioactive iodine into the atmosphere. The build-up of iodine in the thyroid gland can be reduced by taking a medicinal iodine tablet. The effectiveness of the product depends on the correct timing, which is why the iodine tablet must only be taken when instructed by the authorities.

Taking iodine tablets may be appropriate in some areas in Finland if an accident occurs at

  • a nuclear power plant in Olkiluoto or Loviisa
  • the Sosnovyi Bor plant tai Kuolan laitoksella in Russia
  • the Forsmark plant in Sweden.

It is very unlikely that an accident elsewhere would necessitate the protection of the population or the taking of iodine tablets.

Iodine typically builds up in the thyroid gland when it enters the body by inhalation, for example. This is most harmful to people of growing age, where the radiation dose to the thyroid gland can increase the risk of thyroid cancer. The build-up of radioactive iodine in the thyroid gland can be reduced by taking a medicinal iodine tablet. The non-radioactive potassium iodine contained in the tablet fills up the thyroid gland in such a way that it prevents the absorption of radioactive iodine into the gland.

If the air is expected to contain a large amount of radioactive iodine in a particular area of Finland, people are advised to take medicinal iodine tablets. The tablet must only be taken when instructed by the authorities, as the effectiveness of the product depends on the correct timing.

The radioactive substances move with currents of air. The wind speed dictates the velocity of the radioactive plume, and the direction of the wind determines which areas will be contaminated. STUK evaluates the radiation monitoring of the environment and the calculations of the Finnish Meteorological Institute of the atmospheric migration of air currents based on the need for protective measures. If necessary, STUK recommends taking iodine tablets in areas where harmful amounts of radioactive iodine are expected.

Taking iodine tablets in the event of a radiation hazard situation due to a nuclear accident is recommended for people up to 40 years of age, pregnant women or breastfeeding mothers. It is especially important that children and pregnant women or breastfeeding mothers take iodine tablets, because the thyroid glands of children and the foetus are more sensitive to radiation than those of adults. In addition, the thyroid gland of a pregnant woman and breastfeeding mother is enlarged and exceptionally active. If there are not enough tablets, the tablets are given to children and pregnant women. No association between exposure to radioactive iodine and thyroid cancer has been observed in adults; therefore, iodine tablets are not recommended for people over 40 years of age.

According to WHO, studies have not shown that exposure to radioactivity increases the risk of thyroid cancer in people over 40 years of age. The sensitivity of the thyroid gland to the harmful effects of radiation decreases significantly with age.

Correct timing of tablet intake is important. The protective effect of the tablet is reduced if the tablet is taken too early or too late. The emergency services will issue an emergency warning if people should take shelter inside or use iodine tablets.

Sheltering indoors is the primary protective measure in the event of a radiation hazard situation, as it is the most effective way to reduce radiation exposure. Taking iodine tablets is a secondary support measure recommended for people up to 40 years of age, pregnant women and breastfeeding mothers.

Iodine tablets do not protect you against radioactive substances other than iodine. Therefore, sheltering indoors is the primary protective measure.

The iodine tablet only protects the thyroid gland; it does not reduce any other types of radiation exposure. Do not go outside to buy the tablets and become exposed when you have already been advised to stay indoors. Taking cover indoors significantly reduces the amount of radioactive substances entering the body by inhalation, thereby also reducing the dose absorbed by the thyroid gland. Taking iodine tablets is a supplementary protective measure to staying indoors.

Iodine tablets are also available as a food supplement. However, they contain much less iodine than medicinal tablets and are therefore not suitable for use in a radiation hazard situation.

Dosage of iodine tablets for different age groups

  • 130 mg potassium iodide (100 mg iodine) for 12-40-year-olds and pregnant women
  • 65 mg potassium iodide (50 mg iodine) for children aged 3-12 years
  • 32.5 mg potassium iodide (25 mg iodine) for children aged 1 month to less than 3 years
  • 16.25 mg potassium iodide (12.5 mg iodine) for infants less than 1 month of age

You can buy iodine tablets from a pharmacy

Iodine tablets for children over three years of age and adults up to 40 years of age can be bought from pharmacies without a prescription.

Currently, there is no iodine product generally available in Finnish pharmacies that can be accurately administered to children under 3 years of age or under one month of age. The public health care and wellbeing services provide iodine tablets suitable for children under 3 years of age. These tablets are distributed to parents and pregnant women at maternity and child health clinics. In some wellbeing services counties, clinics have pre-announced distribution locations and schedules. Health care providers in the wellbeing services counties will inform about the distribution arrangements when iodine supplementation is available.

Iodine tablets should also be available where children, pregnant women, breastfeeding mothers and adults up to 40 years of age spend longer periods of time. It may be appropriate to maintain stocks of iodine tablets in some public institutions, businesses and communities and their shelters, for example. The authorities recommend that a responsible person be appointed to purchase the products, maintain proper storage conditions for the medicine, and update the stock regularly.

How to use the iodine tablet

  • Only take the iodine tablet when advised by the authorities, to make sure that the timing is right. Instructions will be given on the radio and television. Follow the dosage instructions on the package.
  • Take an iodine tablet especially if you are pregnant or breast-feeding. It is also important to give an iodine tablet to children.
  • Only take one dose. It provides protection for approximately 24 hours. The exposure by inhalation caused by the radioactive plume is likely to only last a couple of hours. If the release recurs or lasts longer, the authorities will advise you on the radio and television to take another dose.

Do not take an iodine tablet

  • if you have hyperthyroidism, dermatitis herpetiformis, or vasculitis with reduced complement levels (hypocomplementemic vasculitis).
  • if you have previously had a serious allergic reaction to iodine.
  • if the thyroid gland has been removed or has not worked, as the iodine tablet protects a functional thyroid gland and is therefore of no use.

Side effects of potassium iodide are very rare. If you have thyroid disease, caution is advised, as some thyroid diseases are associated with a higher risk of side effects. If necessary, talk to your treating physician about taking iodine tablets. The protective role of potassium iodide on the thyroid gland is limited in patients with hypothyroidism receiving thyroxine or other thyroid hormones. If the hypothyroidism is mild and part of the thyroid gland is functioning, an iodine tablet can be taken according to the instructions of the authority.

A previous hypersensitivity reaction caused by contrasting agent that contains iodine does not prevent the use of iodine tablets, as the substance that caused the reaction is likely to be a substance other than iodine. Iodine is an essential nutrient for humans, found in dairy products, eggs, and fish, and it is also added to table salt and cereal products.  

If you have other illnesses or hypersensitivity, or if you are taking other medicines, please read the package leaflet and check with your pharmacist or your physician that this medicine is suitable for you. Only a physician with knowledge of the patient and the disease situation should advise whether the patient should take iodine tablets.


Do you have any questions? Is your question about

  • radiation safety? Send your message to STUK using the online form. [linkki]
  • the health effects of iodine, the administration of iodine tablets or the revised iodine guidelines of the Ministry of Social Affairs and Health? Send your message to the Ministry of Social Affairs and Health by email at kirjaamo.stm (at)
  • iodine tablets as a medicinal product? Send your message to Fimea using the online form​​​​​​​.

If you are not sure if the medicinal iodine tablet is suitable for you, talk to your doctor. Iodine tables should only be taken when advised by the authorities.