What is dehydration?
Dehydration occurs when you don't have enough fluids in your body. Severe dehydration can cause serious problems. If you suspect you are (or someone else is) severely dehydrated, seek medical attention.
You are dehydrated when your body doesn't have enough water to keep it working properly. It can happen when your body loses too much fluid.
When your body has enough water to work properly, you are hydrated.
What are the signs and symptoms of dehydration?
If you have mild to moderate dehydration, you might:
- be thirsty
- have a dry mouth, lips and tongue
- be dizzy or light-headed, particularly when standing up
- have a headache
- have dark urine (wee) and not so much wee as normal
If you have severe dehydration, you might:
- be extremely thirsty
- have a very dry mouth
- be breathing fast
- have a fast heart rate and a low blood pressure
- have a fever
- have little or no urine (wee)
- be irritable, drowsy, or confused
If you experience any symptoms of dehydration, you should:
- move to a cool place
- loosen any tight clothing and remove unnecessary clothes
- drink small amounts of cool water, often
If your symptoms don’t improve seek medical advice.
CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.
What causes dehydration?
People can get dehydrated:
- after strenuous exercise, especially in hot weather
- after severe vomiting or diarrhoea
- with a fever
- after drinking too much alcohol
- while taking certain medicines such as diuretics
- as a complication of diabetes
- if they don’t drink enough water
Anyone may become dehydrated, but babies, young children, older adults, and people with long-term illnesses are at most risk.
When should I see my doctor?
If you, your baby, child, or elderly relative is severely dehydrated, you need to seek urgent medical attention. See your doctor or go to a hospital emergency room.
Complications of dehydration can affect your:
It is important to see your doctor if you are concerned.
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How is dehydration treated?
Severe dehydration needs immediate medical treatment. In hospital, you will get fluids through an intravenous drip.
If you are mildly dehydrated, the best thing you can do is to drink more water. Drink small amounts of water regularly.
You can also drink oral rehydration solutions that you buy from your pharmacy. Or you can make your own rehydration fluids.
Avoid alcohol and caffeine, as they can make dehydration worse.
Recipe to make rehydration fluid
- 6 teaspoons of sugar.
- ½ a teaspoon of salt.
- 1 litre (5 cups) of boiled water.
- Stir the mixture until the salt and sugar dissolve.
Can dehydration be prevented?
Make sure you drink enough water each day.
Have extra fluids:
- during hot weather
- when you’re sick
- when you’re exercising
Water is the best drink to hydrate your body.
As a general guide, adults should drink around 2 to 2.5 litres of fluid a day.
Children should drink around 1 to 2 litres a day.
Dehydration in babies and young children
Babies and young children have a higher risk of becoming dehydrated than adults. Especially if they are sick.
A baby or young child can quickly become dehydrated if they:
- are vomiting
- have a fever
- have diarrhoea
- are unwell for any reason and are not feeding/drinking well
Signs of mild dehydration in babies and toddlers include fewer wet nappies or nappies not as wet as usual. Older children will not go to the toilet as often.
Babies who are severely dehydrated have a sunken fontanel, the soft spot on top of your baby’s head.
See your doctor urgently, or go to the nearest hospital emergency department if your baby or young child:
- is not feeding/drinking well
- is becoming irritable or drowsy
- is pale or has mottled skin
- you are concerned for any reason
Dehydration in older people
Older people can become easily dehydrated because of:
- poor kidney function
- chronic illness
- limited mobility
- certain medicines (particularly diuretics)
Dehydration in the elderly can cause problems such as:
Elderly people need to keep up their fluid intake. They may become dehydrated before they feel thirsty. If you’re caring for an elderly person, you need to remind them to drink regularly.
Resources and support
For more information and support, try these resources:
- Kidney Health — Drink water instead
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Last reviewed: July 2022