When to Call 999 or NHS 111 for Heat Illness

If you think someone has heatstroke, call 999 straight away. That is the advice from Somerset Council, NHS Berkshire Healthcare, Lancaster City Council, South Western Ambulance Service and the North East Ambulance Service, and it does not depend on being certain¹. Heatstroke is a medical emergency: the body can no longer cool itself down and its temperature becomes dangerously high⁶. It can kill, can develop very suddenly and may lead quickly to unconsciousness⁷.

While you wait for the ambulance, keep cooling the person. If they have lost consciousness, put them in the recovery position and carry on cooling them². Do not give them aspirin or paracetamol⁷.

Heat exhaustion is different. It is not usually serious if you can cool down within 30 minutes, but if you suspect it has turned into heatstroke, call 999⁸. If you are worried about heat illness that is not an emergency, NHS 111 is the number to use⁹.

Call 999 straight away if you suspect heatstroke

The threshold is suspicion, not certainty. Every official source on this point says the same thing in slightly different words: if you suspect heatstroke, phone 999 immediately¹; if you suspect someone has heatstroke, call 999²; if you suspect someone is suffering from heat stroke, call 999 immediately⁴. Lancashire Prepared puts it as calling 999 if you suspect heat exhaustion has turned into heatstroke⁸, and the North East Ambulance Service simply says call 999 immediately⁵.

This matters because heatstroke is not a condition you can safely watch at home to see how it develops. The Northern Ireland guidance is blunt: heatstroke can kill, it can develop very suddenly and may lead very quickly to unconsciousness⁷. It is also less common than heat exhaustion but more serious, and it can put a strain on the brain, heart, lungs, liver and kidneys¹⁷.

Calling 999 is also the right move when the picture is unclear. The London Ambulance Service advises that you call 999 if someone is seriously ill or injured, unconscious, having difficulty breathing, or has symptoms of heat stroke⁵. If any of those apply, the call is justified.

Heatstroke signs: confusion, fast breathing and hot skin that is not sweating

The signs of heatstroke are a cluster, and you do not need all of them to act. The UK Health Security Agency broadcast script lists confusion, clumsiness, fast heartbeat, fast breathing or shortness of breath, hot skin and seizures¹⁸. The Mayor of London's guidance gives a similar list: confusion, lack of co-ordination, fast heartbeat, fast breathing or shortness of breath, hot skin that is not sweating, and seizures¹².

For parents, the NHS children's guidance is simpler: call 999 if your child seems confused, breathing fast, has a high body temperature, or is unconscious¹⁹. The Humber and North Yorkshire integrated care board adds skin that is no longer sweating and seizures to that list, and says to put the person in the recovery position and keep trying to cool them down¹¹.

One sign needs a word of its own. NHS guidance describes hot skin that is not sweating and might look red, and notes this can be harder to see on darker skin shades². Do not use skin colour as your test. Use the whole picture: confusion, breathing, heartbeat, co-ordination and whether the person is sweating at all.

Still unwell after 30 minutes of cooling: when heat exhaustion becomes an emergency

Heat exhaustion and heatstroke sit on the same scale, and the 30 minute mark is the practical dividing line. Lancashire Prepared's guidance is that heat exhaustion is not usually serious if you can cool down within 30 minutes, but if you suspect it has turned into heatstroke, call 999⁸. The NHS in Wales says to call 999 if someone is still unwell after 30 minutes of resting in a cool place, being cooled and drinking fluids¹⁴. The Leicester Partnership NHS booklet says the same: if you suspect someone has heatstroke and they are still feeling unwell after 30 minutes of resting in a cool place and drinking plenty of water, call 999¹³.

For a child, the NHS guidance is more specific. Call 999 if a child is still feeling unwell after 30 minutes of resting in a cool place and drinking plenty of water, with signs including confusion, shortness of breath, a high temperature above 40C, not sweating, or loss of consciousness²⁰.

NHS Berkshire Healthcare defines heatstroke in the same terms: it happens when your body cannot cool down and your core temperature gets higher than 40ºC despite resting in a cool place and drinking fluids for 30 minutes or longer². NHS Inform gives the figure as usually more than 40 degrees Celsius²¹.

When NHS 111 is the right call for heat illness

NHS 111 is for urgent problems that are not life-threatening. The Yorkshire Ambulance Service describes it as less urgent than a 999 call¹⁶. Guy's and St Thomas' NHS Foundation Trust says that if you need medical help for a heat-related health problem, contact NHS 111, and that in an emergency, or when you think someone has heatstroke, call 999⁹. The UK Health Security Agency's Beat the Heat guidance says the same: if you are concerned about symptoms, or they are worsening, seek medical advice by contacting NHS 111, and in an emergency, or if you think someone has heatstroke, dial 999¹⁰.

You can reach it by calling 111 or going to 111.nhs.uk, 24 hours a day, seven days a week, including when your GP surgery is closed¹⁵. It can help if you have an urgent medical problem and you are not sure what to do²³. A free NHS 111 BSL service is available for BSL and English interpreter users²⁵.

Heatstroke can come on without warning, so act on suspicion

The most important thing to understand about heatstroke is that it does not always announce itself. The Northern Ireland guidance states that heatstroke can also occur suddenly and without any warning⁷. That is why the official advice is framed around suspicion rather than confirmation: if you suspect it, call 999¹.

The Red Cross guidance for households puts the same message in first aid terms: symptoms include hot, flushed and dry skin, headaches, dizziness or feeling confused or restless, and the help is to call 999 immediately or ask someone else to do it, then quickly move them into a cool place²². If you are on your own with someone who is deteriorating, asking a neighbour to make the call while you cool the person is a sensible division of labour, and the Red Cross explicitly allows for it²².

Heatstroke is also not confined to the very hottest days. The UK experienced a brief but unprecedented extreme heatwave in July 2022, when temperatures in parts of England exceeded 40C for the first time¹⁰, but the risk exists whenever the body cannot shed heat. The practical rule for a household is to know the signs before you need them, and to treat confusion in hot weather as a reason to call rather than a reason to wait.

Where to get help and what happens next

Once you have called 999, the call handler will tell you what to do while you wait. The general first aid advice is to keep cooling the person and to put them in the recovery position if they lose consciousness². Do not give aspirin or paracetamol⁷.

If the person is treated for heatstroke, they will be treated in hospital, and it can take a few days to recover²¹. Heatstroke can strain the brain, heart, lungs, liver and kidneys and can be life-threatening¹⁷, which is why hospital treatment is the expected path once it is suspected.

For heat illness that is not an emergency, NHS 111 is available on 111 or at 111.nhs.uk, 24 hours a day, seven days a week¹⁵. If you need advice about a burn or scald, you can get help from NHS 111²⁶. For anyone who needs extra help in hot weather, including older or disabled people, the Extra Help in an Emergency page explains how to arrange support, and the Heat Exhaustion and Heatstroke page covers the signs in more detail.

For dogs, the RSPCA advises that if a dog is showing any signs of heatstroke, dial 999 at once²⁷. The Pets and Animals in an Emergency page covers wider planning for animals in hot weather.