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 happens when someone loses more fluid than they take in.  The risk is higher in very hot or humid conditions, so make sure you are sipping lots of water at regular intervals and taking other measures to stay cool.

Possible causes include:

  • excess sweating during exercise or sport
  • prolonged exposure to the sun or hot / humid conditions
  • sweating from a raised body temperature. (For example, due to a fever)
  • loss of fluid from severe or persistent diarrhoea and vomiting.

Signs and symptoms 

How to spot dehydration:   

There are four key things to look for if someone is suffering from dehydration: 

  • They may complain of headaches and light headedness
  • Dry mouth, eyes and lips
  • Passing only infrequent amounts of darker urine
  • Have muscle cramps 

Special attention should be paid to babies and young children.  In addition to the above, dehydration may show as pale or mottled skin, sunken eyes, absence of tears when crying or significantly reduced wet nappies.  Young children can deteriorate quickly.  The elderly and those with long-term health conditions may also be more at risk of dehydration during hot weather.

What to do

  1. Treatment of Dehydration:

    Enourage the person to sit down and rest in a cool place.

    Encourage the person to drink plenty of water or other clear fluids.

    Avoid caffeine and alcohol.

  2. Consider the use of oral rehydration sachets which can help replace salt and minerals ther person has lost.  These can be bought from a pharmacy.  Follow the instructions on the packet for the right dose for children and adults.

  3. If dehydration is the result of very hot weather, see the advice on heat exhaustion too.

  4. Keep checking on the person.  If they still feel unwell after rehydrating, or they are not able to keep the fluids down (for example, due to persistant or severe vomiting), encourage them to seek advice.

If left untreated, someone with dehydration can develop heat exhaustion, which is more serious, so it’s important to make sure they rehydrate themselves as soon as possible. 

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At some point in their life, most people will witness or be involved in an accident or medical emergency. Knowing what to do and when you should call the emergency services can potentially save lives.

St John Ambulance volunteers providing support