The short answer
For most UK households, no. Stable iodine (potassium iodide) protects only the thyroid gland, and only from radioactive iodine, which is mainly a risk after an accident at a nuclear reactor. UKHSA says take it only when the authorities tell you to, because timing matters. The US CDC says it will not help in a nuclear bomb emergency, where the danger is fallout outside your body: getting indoors and staying in protects you far more. People who live near UK reactor sites have local plans for tablets. Never take iodised salt or iodine supplements instead.
What iodine tablets actually do
Stable iodine tablets (potassium iodide, sometimes called KI) fill the thyroid gland with ordinary iodine so it can't take up radioactive iodine. That's all they do.
- They protect only the thyroid (UKHSA). They don't protect any other part of the body, and they don't reduce other kinds of radiation exposure.
- Radioactive iodine is mainly a risk after a release from a nuclear reactor. UKHSA's advice covers reactors that are running or have shut down within the last 90 days.
- They work for a short time. UKHSA says one dose protects for 24 hours.
Who needs them, and when
Only the people the authorities tell to take them, at the time they say. UKHSA explains why timing matters:
- They work best from 24 hours before to 2 hours after exposure.
- They can still help up to 8 hours after.
- Don't take them for the first time more than 24 hours after exposure.
- Taking them too early shortens the protection.
The groups who benefit most are children, young people, and pregnant or breastfeeding women. Norway's radiation authority says it's "particularly important" for under-18s and pregnant and breastfeeding women. The UK product information for potassium iodide 65 mg tablets says they're not recommended for people over 40, who are less likely to benefit, except those at risk of a high dose such as emergency workers. The US CDC says the same.
Don't work out doses yourself from a product leaflet. Officials will say who takes how much.
Why they won't help in a nuclear attack
This is the most common mix-up on UK forums. The US CDC is direct: potassium iodide will not help in a nuclear bomb emergency. Fallout contains many radioactive materials that harm you from outside the body. Going out to look for tablets could expose you to dangerous radiation.
What protects you is getting inside a solid building, going to the middle of it, and staying there. Ready.gov says to stay in for at least 24 hours; UKHSA's radiation advice says one to two days, possibly longer. See what to do if there's a nuclear attack warning and which room is safest.
If you live near a nuclear site
Councils around UK nuclear sites plan for this under the REPPIR 2019 regulations. The Office for Nuclear Regulation says each council plans for a Detailed Emergency Planning Zone around the site, and the arrangements are publicised to residents inside it.
One example: Southampton City Council's public plan for the nuclear berth at Southampton Docks says it gives detailed information to everyone within about 1.5 km, outline information to everyone within about 5 km, and that stable iodine tablets are provided to people within 1.5 km, downwind, in an emergency.
If you're not sure whether you're in a zone, check your council's website or its emergency planning team. Use the leaflet and tablets you're given; don't buy your own as a substitute for the local plan.
Never take these instead
- Iodised salt. UKHSA says it should not be taken in place of stable iodine tablets.
- Kelp, seaweed or iodine supplements. The CDC says they're not substitutes and large amounts can be harmful.
- Extra doses. The CDC warns that taking more than recommended can cause severe illness.
Side effects listed by the CDC include stomach upset, rashes and allergic reactions. Anyone with a known iodine sensitivity or thyroid condition should talk to a doctor first.
So what should I buy instead?
For most UK homes, the things that help in any radiation emergency are the same as for a power cut: a battery or wind-up radio to hear official instructions, water and food for a few days indoors, and your medicines. UKHSA says food and tap water already inside your home are considered safe unless you're told otherwise.
We don't link to or sell iodine tablets.
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What to buy
About these links: plain links to ordinary retailer pages. We may earn from some links in future; we don't now. We haven’t tested these and we don’t rank them: they are examples that were in stock when we checked. Prices change. Check what you already own first. Full kit list
Battery or wind-up FM radio
Look for: FM (Be Ready asks for FM; DAB as well is fine). Both a crank and ordinary batteries, so you have two ways to power it.
Bottled water
Look for: 3 litres per person per day for 3 days, for drinking. More for babies, pets and medical devices.
- Seven Oceans Emergency Drinking Water 0.5l (5-year shelf life) · EVAQ8 · £3.94 (price on 1 November 2026) Shop
Frequently asked questions
Should I buy iodine tablets?
Most UK households don't need to. Stable iodine protects only the thyroid from radioactive iodine, which mainly comes from a nuclear reactor accident. UKHSA's advice is to take it only when officials tell you to. If you live near a reactor site, your council's emergency plan covers how tablets reach people in the planning zone.
Should my kids take iodine tablets regularly, just in case?
No. A single dose protects for about 24 hours, so taking it early or regularly doesn't build up protection, and too much can cause harm. The US CDC warns that taking more than recommended can cause severe illness. Children are the group that benefits most in a real reactor emergency, which is why officials will say exactly when and how much.
Do iodine tablets help in a nuclear war?
Not much. The US CDC says potassium iodide will not help in a nuclear bomb emergency, because fallout contains many radioactive materials that harm you from outside the body, and going out to find tablets could expose you to dangerous radiation. Getting inside, staying inside and staying tuned is the protection.
When should you take iodine tablets?
Only when the authorities say so. UKHSA says they work best from 24 hours before to 2 hours after exposure, can still help up to 8 hours after, and shouldn't be taken for the first time more than 24 hours after exposure. Officials will tell you if a second dose is needed.
Can I use iodised salt or kelp instead?
No. UKHSA says iodised salt should not be taken in place of stable iodine tablets, and the CDC says table salt, iodine-rich foods and iodine supplements are not substitutes and large amounts could be harmful.
Is it worth it if I'm over 40?
Usually not. The UK product information for potassium iodide 65 mg tablets says they are not recommended for people over 40, who are less likely to benefit, except people at risk of a high dose such as emergency workers. The CDC and Norway's radiation authority say the same.
Sources
We opened each page on the date shown. Official advice changes: if a source says something different now, follow the source.
- UKHSA (GOV.UK): What to do in a radiation emergency (updated 10 September 2024) (read 1 November 2026)
- US CDC: Potassium iodide (KI) (read 1 November 2026)
- Electronic Medicines Compendium: Potassium iodide 65 mg tablets, summary of product characteristics (read 1 November 2026)
- Norwegian Radiation and Nuclear Safety Authority (DSA): Taking iodine tablets in the event of a nuclear accident (read 1 November 2026)
- Office for Nuclear Regulation: Local emergency arrangements (read 1 November 2026)
- Southampton City Council: Reactor emergency plan, public version (REPPIR 2019) (PDF) (read 1 November 2026)
- Ready.gov (FEMA): Nuclear explosion (read 1 November 2026)
Related guides
- Radiation emergency in the UK: what official advice says (go in, stay in, tune in)
- Worried about war? How UK households can prepare — calmly
- UK Emergency Alerts: a calm guide
We're an independent UK site, not the government. We check guides against official sources and link to them. In an emergency call 999.
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