Heat stroke and heat exhaustion

Heat stroke happens when your body temperature gets too high due to being exposed to too much heat.

Key points about heat stroke and heat exhaustion

  1. When you are exposed to too much heat, your body has protective mechanisms that help to keep your temperature normal. When this happens you will feel the symptoms of heat exhaustion. 
  2. If you stay in the sun for longer, your body struggles to cope with the extra heat. Once your temperature rises to over 40 degrees C, you will have heat stroke. 
  3. Heat stroke is an emergency and needs to be treated immediately.
  4. There are things you can do to help prevent heat stroke and heat exhaustion, including to drink plenty of water, especially during hot weather or exercise. 

If you or someone you care for has any of the following symptoms, call 111 for an ambulance or go to the nearest emergency department immediately:

  • high temperature over 40 degrees C
  • severe nausea (feeling sick) or vomiting (being sick)
  • severe headache
  • fast pulse
  • shallow and fast breathing
  • very hot and flushed skin
  • weak or cramping legs and arms
  • not sweating despite being very hot
  • dizziness, feeling faint or fainting
  • confusion or agitation
  • seizures or fits
  • collapse or loss of consciousness (not responding to you).

What are the causes of heat stroke and heat exhaustion?

When you are exposed to too much heat, your body has protective mechanisms that help to keep your body temperature normal. This is important as a lot of internal processes in your body require normal body temperature to work well. 

If you get too hot, you will experience symptoms (as listed below) as your body's protective mechanisms start to kick in. Your body will react by:

  • sweating to lose more heat
  • making your urine (pee) darker and concentrated (your body is trying to preserve more water)
  • making you feel thirsty. 

Your body is trying to tell you to get out of the sun or extreme heat. This is called heat exhaustion.

If you stay in the sun for longer, your body will struggle to cope with the extra heat. All the protective mechanisms start to give up and your temperature will rise to over 40 degrees. When this happens, it's called heat stroke.

Heat stroke is a medical emergency and you need to call an ambulance or go to the nearest emergency department immediately. 

Who is at risk of heat stroke and heat exhaustion?

People who are at higher risk of heat stroke and heat exhaustion include:

What are the symptoms of heat stroke and heat exhaustion?

Common symptoms of heat exhaustion include:

  • high temperature over 40 degrees C
  • severe nausea (feeling sick) or vomiting (being sick)
  • severe headache
  • fast pulse
  • shallow and fast breathing
  • very hot and flushed skin
  • weak or cramping legs and arms
  • not sweating despite being very hot
  • dizziness, feeling faint or fainting
  • confusion or agitation
  • seizures or fits
  • collapse or loss of consciousness (not responding to you). 

If you or someone you care for has any symptoms of heat stroke, call 111 for an ambulance or go the nearest emergency department immediately.

How is heat stroke and heat exhaustion treated?

Heat stroke is a medical emergency and needs to be treated immediately by doctors. Call 111 for an ambulance or go to the nearest emergency department immediately if someone you care for has symptoms of heat exhaustion or heat stroke. 

There are things you can do to help the person while waiting for an ambulance or on the way to the nearest emergency department. These include to:

  • move them to a cool place and lay them down
  • get them to drink plenty of water or an isotonic (sports or energy) drink
  • stay with them at all times
  • remove as much clothing as possible 
  • put them in a cool bath or shower if possible
  • cool their skin by wetting with cool water or fan them, or apply cold packs around their armpits or neck
  • put them in the recovery position if they lose consciousness. Read more about the recovery position

How can I prevent heat stroke and heat exhaustion? 

There are things you can do to help prevent heat stroke and heat exhaustion, especially during hot weather or exercise. These include:

  • drink plenty of fluids 
  • avoid too much alcohol
  • avoid extreme or intense exercise in hot weather
  • avoid hot sun during the middle of the day
  • take cool baths or showers
  • wear loose clothing 
  • keep your home cool
  • keep indoor plants to help cool the air. 

Learn more

Heat and sun injuries HealthInfo Canterbury, NZ 
Heat exhaustion and heatstroke Patient Info, UK
Heat exhaustion and heatstroke NHS, UK

References

  1. Heat exhaustion and heatstroke Patient Info, UK
  2. Heat exhaustion and heatstroke NHS, UK

Reviewed by

Dr Alice Miller trained as a GP in the UK and has been working in New Zealand since 2013. She has undertaken extra study in diabetes, sexual and reproductive healthcare, and skin cancer medicine. Alice has a special interest in preventative health and self-care, which she is building on by studying for the Diploma of Public Health with the University of Otago in Wellington.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Alice Miller, FRNZCGP Last reviewed: 13 Jan 2021