What is dehydration?

Dehydration means your body does not have enough fluid. This may be because you haven't drunk enough fluid to replace the fluids you have lost, such as when sweating or in your wee (urine). If dehydration isn't treated it can get worse and become a serious problem.

The symptoms include:

• Feeling thirsty.

• Dark yellow and strong-smelling wee (urine).

• Feeling dizzy or light-headed.

• Sentindo-se muito cansado.

• Dry mouth, lips and eyes.

• Weeing less urine and less often.

However the symptoms and signs vary depending on age and the severity of dehydration.

Signs in adults

• Thirst.

• Dry or sticky mouth.

• Not peeing very much.

• Dark yellow pee.

• Dry, cool skin.

• Dor de cabeça.

• Cãibras musculares.

Signs of severe dehydration

• Not peeing, or having very dark yellow pee.

• Very dry skin.

• Sentir-se tonto.

• Rapid heartbeat.

• Respiração rápida.

• Olhos fundos.

• Sleepiness, lack of energy, confusion or irritability.

• Desmaio.

The causes include:

• Not drinking enough fluids.

• Sentir-se mal (vômito).

• Diarreia.

• Being exposed to the sun in hot weather for long periods ('sunstroke').

• Beber muito álcool.

• Excess sweating.

• Alta temperatura (febre).

• Taking certain medicines called diuréticos that reduce the amount of fluid in your body.

Babies, young children, the elderly and people with diabetes are at increased risk of dehydration.

Do coffee and tea dehydrate you?

Coffee and tea contain caffeine, which has a slight diuretic effect (making you want to wee more). However, you would have to drink large amounts of each for this to be significant. The fluid in the tea or coffee will usually counteract this effect.

Drinking lots of fluids

If it's difficult to drink or you keep being sick (vomiting) then keep taking small sips of fluid and gradually drink more if you can.

Rehydration sachets

These are only recommended for those who are at increased risk of dehydration - for most people, drinking normal fluids such as water is fine.

Speak with your doctor or nurse for advice if your symptoms don't improve or you have any concerns. Call 111 (in the UK) if you can't speak to your GP or don't know what to do next.

Call 999 (in the UK) or go to Accident and Emergency (A&E) if you have any signs of severe lack of fluid in the body (dehydration), such as:

• Feeling very weak and tired.

• Feeling confused or disorientated.

• Tontura.

• Not having passed wee (urine) for eight hours.

• Your pulse feeling weak and rapid.

It's quite common for young children to become lacking in fluid (dehydrated). It is often mild but can be serious if it's not dealt with quickly. Babies and young children need plenty of fluids to avoid dehydration.

Signs of dehydration in babies, infants, toddlers and young children

The signs of dehydration include:

• Dry mouth and tongue

• No tears when crying

• Dry nappies for over 3 hours

• Sunken eyes and cheeks

• Sunken soft spot on the top of the skull (fontanelle) in babies

• Sleepiness, lack of energy, or irritability

Treatment of dehydration in babies and young children

• You should continue breastfeeding or using formula. Give smaller quantities of milk more often than usual. Don't make formula weaker by diluting it with water.

• Give small children their usual diet.

• Give frequent small sips of extra water.

• Rehydration powder sachets are only needed if the child is at increased risk of dehydration - normal fluids are fine for most children.

Contact your doctor urgently or call an ambulance if your child displays any of the following signs or symptoms of dehydration:

• Seems drowsy.

• Is breathing fast.

• Has a dry mouth.

• Has dark-yellow wee.

• Has cold and blotchy-looking hands and feet.