News: Heat exhaustion and heatstroke 

Heat exhaustion and heatstroke are two heat-related health conditions. If they're not quickly treated, they can both be very serious.

Heat exhaustion

Heat exhaustion can occur when the temperature inside the body (the core temperature) rises to anything between the normal 37°C (98.6°F) up to 40°C (104°F). 

At this temperature, the levels of water and salt in the body begin to fall, which can cause a person to feel sick, feel faint and sweat heavily.

If a person with heat exhaustion is taken quickly to a cool place, is given water to drink and has their excess clothing removed, they should begin to feel better within half an hour and have no long-term complications.

Without treatment, they could develop heatstroke.

Certain groups are more at risk of developing heatstroke or suffering complications from dehydration, and should be taken to hospital. This includes: 

  • children under two years old
  • very elderly people
  • people with kidney, heart or circulation problems
  • people with diabetes who use insulin


Heatstroke is far more serious than heat exhaustion. It occurs when the body can no longer cool itself and starts to overheat.

When the core temperature rises above 40°C (104°F) the cells inside the body begin to break down and important parts of the body stop working.

If left untreated, it can lead to complications, such as organ failure and brain damage. Some people die from heatstroke.

The symptoms of heatstroke can include:

  • mental confusion
  • rapid shallow breathing (hyperventilation)
  • loss of consciousness

What to do

Heatstroke is a medical emergency and should be treated immediately. Dial 999 to request an ambulance if you suspect heatstroke. 

While you're waiting for an ambulance to arrive, make sure that the person is as cool as possible. Move them to a cool area as quickly as possible, remove excess clothing and try to cool them by fanning them. If they're conscious, give them cool, not cold, water to drink.

Who's at risk?

Heatstroke can affect anyone, but some people are more at risk than others and should take extra precautions during warm weather, especially during a heatwave. These include:

  • the elderly
  • babies and young children
  • people with conditions that affect the body's ability to cool down, such as diabetes
  • those who have drunk too much alcohol (which dehydrates the body)
  • people on certain drugs and medications, such as antipsychotics and betablockers
  • people who might find it difficult to keep cool during a heatwave – for example, those who are bed-bound or disabled.

Avoiding heat exhaustion and heatstroke

There are steps you can take to reduce the risk of heat exhaustion and heatstroke during a heatwave:

  • Stay out of the sun during the hottest parts of the day, particularly between 11am and 3pm.
  • If you have to go out in the heat, walk in the shade, apply sunscreen and wear a hat.
  • Don't leave anyone in a parked car.
  • Avoid extreme physical exertion.
  • Have plenty of cold drinks, but avoid drinks that contain caffeine and alcohol.
  • Eat cold foods, particularly salads and fruit with a high water content.
  • Take a cool shower, bath or body wash.
  • Sprinkle water over your skin or clothing, or keep a damp cloth on the back of your neck.
  • Keep your environment cool.

Article: From NHS Choices