potassium iodide at a glance
Medicine class
Antidote and thyroid-blocking agent
Main use
Thyroid protection following an official warning about radioactive iodine release
Important limitation
It does not protect against external radiation or radioactive substances other than iodine.
What is potassium iodide used for?
The selected UK product is licensed for use after a nuclear accident releasing radioactive iodine.
Prevention of radioactive iodine uptake by the thyroid after inhalation or ingestion, when authorities advise its use.
How does potassium iodide work?
The thyroid naturally collects iodine. Potassium iodide temporarily fills this uptake pathway with stable iodine, reducing radioactive iodine accumulation and radiation exposure to the thyroid. It does not remove other radionuclides or shield the rest of the body.
potassium iodide preparations and strengths
Tablet
Route: Oral
Strengths: 65 mg
How to take potassium iodide
Take potassium iodide only when government or emergency services explicitly instruct, and follow the supplied leaflet. Do not substitute iodised salt, dietary supplements or other iodine products.
The scored tablet may be chewed or swallowed whole.
For babies and young children, it can be ground or dispersed in water, syrup or a similar liquid.
Continue following official advice about sheltering, evacuation, food and water.
potassium iodide side effects
Common or expected effects
- Reported effects of uncertain frequency include stomach upset, headache, and swollen or inflamed salivary glands.
Get urgent medical advice
- Bronchospasm or another severe hypersensitivity reaction.
- New or worsening overactive or underactive thyroid function, thyroid inflammation or thyroid enlargement.
- Severe throat swelling or breathing difficulty, particularly after excessive ingestion.
potassium iodide in pregnancy
Pregnant women may be prioritised for thyroid protection when authorities advise it because radioactive iodine can affect maternal and fetal thyroids. Repeated iodine exposure can suppress fetal thyroid function; tell the maternity team after use, particularly later in pregnancy, as newborn thyroid assessment may be needed.
potassium iodide while breastfeeding
Breastfeeding can continue when potassium iodide is required. Iodine passes into milk, but this does not provide sufficient thyroid protection for an exposed baby, who needs separate instructions from emergency or healthcare professionals.
potassium iodide interactions
Relevant interactions mainly involve thyroid procedures or medicines that can increase blood potassium.
Radioiodine treatment or thyroid diagnostic tests
Can interfere with radioiodine uptake and affect treatment or test results.
ACE inhibitors, potassium-sparing diuretics and aldosterone antagonists
May increase the risk of high blood potassium.
Quinidine
Raised potassium concentrations may enhance quinidine’s effects on the heart.
Common questions about potassium iodide
Answers are fully visible for fast scanning and source review.
What radiation does potassium iodide protect against?
It reduces thyroid uptake of radioactive iodine. It does not protect against external radiation or other radioactive substances.
Should it be taken before any emergency warning?
No. Take it only when government or emergency services explicitly instruct, because timing and location determine whether it is beneficial.
Can iodised salt replace the tablets?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.