What is dehydration?
Dehydration occurs when you don't have enough fluids in your body. If severe, dehydration can cause serious problems. If you suspect you are (or someone else is) severely dehydrated, seek medical attention.
You are dehydrated if your body doesn't have enough water to keep it working properly. It can happen when your body loses too much fluid, such as from excessive sweating.
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
- have a headache
- have dark urine, and not so much of it
- be dizzy or light-headed, particularly when standing up
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
- be irritable, drowsy or confused
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 or have a fever or diarrhoea. As well as those listed above, 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 a baby’s head.
If your baby or young child shows signs of severe dehydration or you are concerned for any reason, see your GP or go to the nearest emergency department.
Dehydration in older people
Older people can become easily dehydrated because of:
- declining kidney function
- chronic illness
- limited mobility
Dehydration in the elderly can cause problems such as confusion, constipation, dizziness and weakness. 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 may need to remind them to drink regularly.
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.
How is dehydration treated?
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 purchased from the pharmacy or make your own (6 teaspoons of sugar with half a teaspoon of salt in one litre of boiled water). Here are instructions. Avoid alcohol and caffeine, as they can make you more dehydrated.
When should I see my doctor?
Severe dehydration needs immediate medical treatment, usually in hospital where fluids are given through an intravenous drip.
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.
Can dehydration be prevented?
Make sure you drink enough water each day, and have extra to replace any fluid lost during hot weather, illness or exercise. Water is the best drink to hydrate the body. As a general guide, adults should drink around 2 to 2.5 litres of fluid a day and children should drink around 1 to 2 litres a day.
Resources and support
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Last reviewed: March 2020