Dehydration

4-minute read

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

Urine colour chart — Use this urine colour chart to assess how hydrated you are.

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 elderly people

Elderly people can become easily dehydrated because of:

declining kidney function
chronic illness
limited mobility
medication

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.