Déshydratation
Revu par Dr Colin Tidy, MRCGPDernière mise à jour par Dr Toni Hazell, MRCGPLast updated 30 juil. 2024
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Although dehydration can be mild and usually just needs you to drink extra fluids, it can also be very severe and life-threatening.
At a glance
Dehydration means your body does not have enough fluid.
Symptoms can include thirst, dark urine, dizziness, and a dry mouth.
Causes include not drinking enough, vomiting, diarrhoea, or excessive sweating.
Babies, young children, older adults, and people with diabetes are at higher risk.
Drink plenty of fluids to treat dehydration; rehydration sachets may be used if recommended.
Seek urgent medical help for signs of severe dehydration, especially in children.
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Qu'est-ce que la déshydratation ?
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.
Signs and symptoms of dehydration
Retour au sommaireThe symptoms include:
Feeling thirsty.
Dark yellow and strong-smelling wee (urine).
Se sentir étourdi ou léger.
Feeling very tired.
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.
Maux de tête.
Crampes musculaires.
Signs of severe dehydration
Not peeing, or having very dark yellow pee.
Very dry skin.
Sensation de vertige.
Rapid heartbeat.
Respiration rapide.
Yeux enfoncés.
Sleepiness, lack of energy, confusion or irritability.
Évanouissement.
Severe dehydration is a medical emergency and needs immediate treatment.
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What are the causes of dehydration?
Retour au sommaireThe causes include:
Not drinking enough fluids.
Being exposed to the sun in hot weather for long periods ('sunstroke').
Drinking too much alcohol.
Taking certain medicines called diurétiques 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.
What are the treatments for dehydration?
Retour au sommaireDrinking 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.
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When to see a doctor for dehydration
Retour au sommaireSpeak 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.
Vertiges.
Not having passed wee (urine) for eight hours.
Your pulse feeling weak and rapid.
Babies and young children with dehydration
Retour au sommaireIt'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.
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Questions fréquemment posées
What is the primary cause of dehydration?
Dehydration is mainly caused by not drinking enough fluids to replace those lost through processes like sweating or urination. Other contributing factors can include vomiting, diarrhoea, significant exposure to heat, excessive alcohol consumption, and having a high temperature.
Can I get dehydrated if I'm not doing strenuous exercise?
Yes, you can become dehydrated even if you are not exercising. Not drinking enough fluids throughout the day can lead to dehydration. Factors like hot weather, vomiting, diarrhoea, or a fever can also cause dehydration without strenuous activity.
Are there specific groups of people who are more vulnerable to dehydration?
Yes, certain groups are at a higher risk of dehydration. These include babies, young children, older adults, and individuals with diabetes. Additionally, people taking certain diuretic medications may also be more susceptible to dehydration.
How can I tell the difference between mild and severe dehydration in an adult?
Mild dehydration in adults typically presents with symptoms such as thirst, dry mouth, less frequent urination, dark yellow pee, cool skin, headache, and muscle cramps. Severe dehydration is more serious and includes signs like not peeing at all or very dark pee, very dry skin, dizziness, rapid heartbeat and breathing, sunken eyes, sleepiness, confusion or irritability, and fainting.
If I am feeling sick or vomiting, what is the best way to rehydrate myself?
If you are finding it difficult to drink or are vomiting, you should try to take small sips of fluid frequently. Gradually increase the amount you drink if you can tolerate it. For most people, drinking normal fluids like water is effective.
When should I use rehydration sachets instead of just water?
Rehydration sachets are generally recommended for individuals who are at an increased risk of dehydration. For most people, simply drinking normal fluids such as water is sufficient. In children, rehydration sachets are only needed if the child is at increased risk.
What are the specific signs of dehydration to look out for in a baby?
Signs of dehydration in babies, infants, toddlers, and young children include a dry mouth and tongue, no tears when they cry, dry nappies for over three hours, sunken eyes and cheeks, a sunken soft spot (fontanelle) on the top of their head, and being sleepy, lacking energy, or irritable.
Lectures complémentaires et références
- Diarrhée et vomissements chez les enfants de moins de 5 ans; Ligne directrice clinique NICE (avril 2009; mise à jour octobre 2022).
- Gastro-entérite; NICE CKS, mai 2024 (accès réservé au Royaume-Uni)
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About the authorView full bio

Dr Toni Hazell, MRCGP
MBBS, BSc, MRCGP, DFSRH, Dip GU med, DRCOG, DCH (London, UK, 2000)
Dr. Toni Hazell qualified from St. Mary’s Hospital Medical School and did her VTS at Northwick Park Hospital.
About the reviewerView full bio

Dr Colin Tidy, MRCGP
Médecin généraliste, Auteur médical
MBBS, MRCGP, MRCP (Paediatrics), DCH
Dr Colin Tidy is an NHS Doctor, based in Oxfordshire.
Historique de l'article
Les informations sur cette page sont rédigées et examinées par des cliniciens qualifiés.
Prochaine révision prévue : 30 juil. 2027
30 juil. 2024 | Dernière version

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