When your baby has diarrhoea, vomiting, a fever or simply refuses feeds on a hot day, the worry is whether they are getting enough fluid. Babies lose water quickly and cannot tell you they are thirsty. Knowing the signs of dehydration in babies helps you act early, before it becomes serious.
Quick answer: dehydration in babies
- Early signs: fewer wet nappies, darker urine, a dry mouth and fewer tears.
- Serious signs: a sunken soft spot, sunken eyes, cold hands and feet, unusual sleepiness or floppiness.
- Prevent it by offering frequent breast or formula feeds during illness and hot weather.
- Babies under 6 months with signs of dehydration should be seen by a doctor the same day.
Common causes
- diarrhoea and vomiting. See vomiting and diarrhoea in babies
- fever, which increases fluid loss
- refusing feeds because of a sore mouth, blocked nose or illness
- hot weather or overheating
Signs to watch for
- Mild to moderate: fewer than 4 to 6 wet nappies in 24 hours, dark or strong-smelling urine, dry lips and mouth, fewer tears when crying, more irritable than usual.
- Severe: no wet nappy for 6 to 8 hours or more, sunken soft spot or eyes, very sleepy or hard to wake, cold or mottled hands and feet, fast breathing.
What to do
- Keep feeding. Breastfeed more often, or offer formula in smaller, more frequent amounts.
- Ask your doctor or pharmacist about oral rehydration solution, especially with diarrhoea and vomiting.
- Do not give plain water to babies under 6 months, or fruit juice or sports drinks.
- Count wet nappies and note what your baby takes in.
- Keep your baby cool in hot weather.
Preventing dehydration in hot weather
- offer extra feeds; babies over 6 months can have sips of water too
- keep your baby in the shade and dress them lightly
- never leave a baby in a parked car
See keeping baby cool.
When to talk to your doctor
- any signs of dehydration in a baby under 6 months
- no wet nappy for 6 hours or more
- sunken soft spot or eyes, cold hands and feet, or unusual sleepiness: seek urgent help
- vomiting everything, green vomit or blood in poo
- fever in a baby under 3 months
Frequently asked questions
How do I count wet nappies with disposables?
Modern nappies are very absorbent. Put a tissue inside, or compare the weight with a dry nappy.
Can teething cause dehydration?
Not directly, but a sore mouth can make babies drink less. Keep offering feeds.
When should I use rehydration solution?
Ask your doctor or pharmacist; they will advise how much to give for your baby’s age.
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Sources
- NHS: Dehydration
- NICE: Diarrhoea and vomiting caused by gastroenteritis in under 5s
- American Academy of Pediatrics, HealthyChildren.org: Dehydration
This guide is general information, not medical advice. If you think your baby is dehydrated, contact your doctor straight away.