Dehydration in babies and children: signs, assessment and rehydration in the UK

Dehydration means the body is losing more fluid than it takes in. In children this is most often because of diarrhoea and vomiting from a stomach bug, but it can also follow a high temperature, hot weather, heavy sweating, or simply not drinking enough while unwell. The NHS says babies, children and older adults are more at risk.

Young children have smaller fluid reserves than adults, so a short illness can matter more. They also rely on someone else to offer drinks and often refuse fluids when feeling sick. That is why guidance for parents focuses on small, frequent amounts of fluid and on recognising early signs, rather than waiting until a child is obviously unwell.

The NHS describes symptoms common to adults and children, including thirst, headache, dizziness, dark yellow and strong-smelling urine, peeing less often, tiredness, and a dry mouth, lips and tongue. In babies it lists specific signs that parents can check at home.

• A sunken soft spot on top of the head (the fontanelle).

• Sunken eyes.

• Few or no tears when they cry.

• Fewer wet nappies than usual.

• Being drowsy or unusually irritable.

• Breathing quickly or a fast heart rate, which the NHS includes among the signs that need urgent advice.

NICE guidance on diarrhoea and vomiting in under 5s identifies groups at increased risk of becoming dehydrated. Knowing the list helps parents decide when to call for advice early rather than late.

• Children younger than 1 year, particularly those younger than 6 months.

• Infants who were of low birth weight.

• Children who have passed more than five diarrhoeal stools in the previous 24 hours.

• Children who have vomited more than twice in the previous 24 hours.

• Children who have not been offered, or have not been able to tolerate, extra fluids.

• Infants who have stopped breastfeeding during the illness.

• Children with signs of malnutrition.

NICE guidance sorts children into three groups: no clinically detectable dehydration, clinical dehydration and clinical shock. The assessment combines how the child looks and behaves with examination findings, interpreted in the light of the risk factors above. Shock is the most serious group and needs emergency care.

The first questions can be asked remotely, for example on an NHS 111 call: does the child appear unwell, is their responsiveness altered (irritable or lethargic), is urine output reduced, is the skin pale or mottled, and do the hands and feet feel cold. A face-to-face examination adds other signs such as sunken eyes, dry mucous membranes, fast heart rate, fast breathing, weak pulses and slow capillary refill.

For a child who is not dehydrated, the NHS and NICE advise carrying on usual feeds, including breast or formula milk, encouraging plenty of fluids and avoiding fruit juice and fizzy drinks, which can make diarrhoea worse. A pharmacist can recommend oral rehydration solution, which is a powder mixed with water, and NICE suggests offering it as an extra drink to children at higher risk.

When a child is clinically dehydrated, NICE says rehydration is usually possible with oral rehydration solution given frequently in small amounts, with the volume calculated by the clinician over about 4 hours, alongside continued breastfeeding. A tube through the nose is sometimes used if a child cannot or will not drink it. Intravenous fluids are used if the child is in shock, if they deteriorate despite oral rehydration, or if they keep vomiting the solution.

After rehydration NICE recommends full-strength milk straight away and the child's usual diet, with fruit juice and fizzy drinks avoided until diarrhoea has stopped. Antibiotics are not routinely given for gastroenteritis, and NICE says not to use antidiarrhoeal medicines.

NICE says diarrhoea in children usually lasts 5 to 7 days and in most stops within 2 weeks, while vomiting usually lasts 1 to 2 days and in most stops within 3 days. The NHS gives similar timings. Seek advice if symptoms last longer than this.

The NHS advises washing hands with soap and water, washing soiled clothing and bedding separately, and keeping children off nursery or school until they have not been sick or had diarrhoea for at least 2 days. It also says not to use a swimming pool until at least 48 hours after symptoms stop. The older NICE under-5s guideline gives 2 weeks for swimming, so if in doubt follow the current NHS wording or ask your pharmacist or GP.

Call NHS 111 if you are worried about a baby under 12 months, if your child stops breast or bottle feeding while ill, if a child under 5 has signs of dehydration such as fewer wet nappies, if they keep being sick and cannot keep fluid down, if there is bloody diarrhoea, or if diarrhoea lasts more than 7 days or vomiting more than 2 days. The NHS also says to call 111 for advice about a child under 5 with dehydration signs.

Call 999 or go to A&E if your child vomits blood or has vomit that looks like ground coffee, has yellow-green or green vomit, may have swallowed something poisonous, has a stiff neck and pain looking at bright lights, has a sudden severe headache or tummy ache, has blue, grey, pale or blotchy skin, lips or tongue, is breathing with severe difficulty or very fast, or is confused or not responding as usual. Do not drive yourself if you are alone with a very unwell child; call 999 for an ambulance.

Most children with dehydration from a stomach bug are seen through NHS routes: pharmacy advice, NHS 111, a GP, or an emergency department when they are seriously unwell. NICE suggests that children in the clinically dehydrated group may be reviewed face to face, and that parents are given clear information about warning signs and who to contact if they appear.

Private paediatric services exist, but in an emergency the right place is the nearest emergency department or an ambulance. The signs of shock described above are not situations to wait out for an appointment.