Emergency advice


  1. Sit them down.
  2. Drink lots of water.
  3. Advise rest.
  4. Stretch and massage muscles to ease cramp.
  5. If they're unwell seek medical advice.

What is dehydration?

Dehydration occurs when someone loses fluid from the body and does not replace it. If untreated, someone with dehydration can develop heat exhaustion.

Possible causes include:

  • excess sweating during exercise
  • too much exposure to the sun or humid conditions
  • sweating from a raised body temperature. For example, a fever
  • loss of fluid from severe diarrhoea and vomiting.

Signs and symptoms 

Look for:

  • a headache or light-headedness
  • dizziness or confusion
  • a dry mouth and dry eyes
  • dry or cracked lips
  • reduced amounts of dark urine
  • muscle cramps, such as to the calves.

Special attention should be paid to babies and young children as they may also have pale skin with sunken eyes and can deteriorate very quickly.

What to do

  1. Reassure the casualty and help them to sit down.

  2. Give them plenty of water. You can also use an oral rehydration solution. These can help to replace fluid as well as the correct salt and other minerals they’ve lost.

    • Do not mix regular cooking salt into water and give it to the casualty, this will make the condition worse.
  3. If they have any painful cramps, encourage them to rest. Help them to stretch and massage the muscles that are affected.

  4. Monitor the casualty’s level of response.

    • If the casualty appears to be unwell, seek medical advice.

Our training courses:

First aid courses

First aid courses


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St John Ambulance volunteers providing support