Heatstroke

Dr Lynn Thomas, OStJ, BSc, MB.BS, MA, FRCPClinically reviewed: 28/04/2025

Heatstroke is more serious than heat exhaustion and can be life-threatening.

What is heatstroke?

Heatstroke is caused by a failure of the 'thermostat' in the brain which regulates the body’s temperature. This means the body is unable to cool down when it becomes too hot.

It can be caused by spending too much time in the sun, having a high fever, or from taking recreational drugs such as ecstasy. It can also occur after heat exhaustion when sweating ceases.

Your priority is to cool the casualty down as quickly as possible and get them to hospital.

Signs and symptoms

Look for:

headache, dizziness, and discomfort 
restlessness, confusion, or unusual behaviour
hot flushed and dry skin
fast deterioration in the level of response
a full bounding pulse   
body temperature above 40°C (104°F).

What to do

1
Move them to a cool, shaded place and remove their outer clothing if possible.
2
Call 999 or 112 for emergency help.
3
Sit them down and wrap them in a cool, wet sheet. If there isn’t a sheet available, fan them or sponge them down with cold water to keep them cool. If available, use cold packs placed in the armpits and around the neck.
4
Once their temperature seems to have gone back to normal, replace the wet sheet with a dry sheet.
5
While waiting for help to arrive, keep checking their temperature, as well as their breathing, pulse, and level of response.
Be prepared to put them in the recovery position if they become unresponsive.
6
If they start getting hot again, repeat the cooling process to lower their temperature.
Occasionally, someone with heatstroke may experience seizures. Be prepared to recognise and treat these as appropriate.