Dehydration means your baby is losing more fluid than they're taking in, usually because of vomiting, diarrhoea, a fever or feeding less while unwell. The first signs are fewer wet nappies, darker wee, a dry mouth and a baby who is quieter than usual. The Royal Children's Hospital Melbourne (RCH) says any baby under 6 months with a sign of dehydration should see a doctor, because they can get sicker very quickly. Sunken eyes, cold or mottled skin, a very sleepy baby or no wet nappy for 12 hours mean emergency care now.
This guide covers how to check your baby, what to offer while you arrange help, and which signs belong in which tier. The tiers match our when to call the doctor guide.
What are the signs of dehydration in a baby?
Signs build from small changes to serious ones. The RCH, the NHS and the American Academy of Pediatrics (AAP) describe similar stages:
| Stage | What you might notice | What to do |
|---|---|---|
| Early | Fewer wet nappies than usual; older babies may seem thirsty | Offer more feeds; under 6 months, see a doctor today |
| Moderate | Darker wee, dry mouth and lips, fewer or no tears, quieter than usual, cool hands and feet | Get medical help today |
| Severe | Sunken eyes or soft spot, cold mottled hands and feet, very sleepy or floppy, little or no wee | Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) or go to emergency now |
The AAP counts fewer than 6 wet nappies a day in an infant as a sign of mild to moderate dehydration, and says to tell your baby's doctor straight away if any warning sign appears. Its list of severe signs adds being very fussy, wrinkled skin and weeing only once or twice a day. The RCH warns that severe dehydration is serious and can get worse quickly.
The NHS lists a soft spot (fontanelle) that sinks inwards, and few or no tears when crying, as reasons for an urgent GP appointment. Our guides are stricter about the soft spot and put it in the emergency tier alongside sunken eyes. Fewer tears on their own are a same-day sign.
How many wet nappies should my baby have?
Wet nappies are the easiest sign to check at home. As a guide, the AAP treats fewer than 6 wet nappies a day as a warning sign. In the first week, when the count builds up day by day, see is my baby getting enough milk? for what to expect.
| What you notice | What to do |
|---|---|
| Fewer wet nappies than usual, or darker yellow wee | Get medical help today |
| Only 1 or 2 wet nappies in a day | Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) or go to emergency now |
| No wet nappy or wee for 12 hours | Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) or go to emergency now |
The NHS urgent-help guide lists not having a wee in the past 12 hours among the reasons to call an ambulance or go to A&E.
Modern disposable nappies soak wee away from the skin, so a wet one can feel dry. Many parents find it easier to judge by weight, comparing a used nappy with a clean one. If your baby has runny poo, it can be hard to tell wee from diarrhoea, so say so when you call.
Why do babies get dehydrated so easily?
The RCH says babies and young children are most at risk because they lose more fluid through their skin, depend on others for drinks and can't tell you when they need more. Common causes it lists are:
- gastroenteritis (gastro), the most common cause, through vomiting, diarrhoea and eating and drinking less
- other viral infections, including colds that make feeding hard (see colds and congestion)
- a sore mouth or throat, such as hand, foot and mouth disease, that makes drinking painful
- high fevers, through sweating (see fever in babies)
- hot weather and too much sun (see hot weather)
- long-term heart, kidney or gut conditions, and medicines such as diuretics
The RCH gastro fact sheet says babies under 6 months are at higher risk, and should see a doctor or health professional if they show signs of gastro. For what runny or unusual poo can mean, see baby poo.
What should I give my baby if they're getting dehydrated?
These steps are for while you arrange help, or after a doctor has seen your baby. They're never a reason to delay care for a baby under 6 months.
- Keep breastfeeding, and feed more often. The RCH gastro fact sheet says you can also give oral rehydration solution for the first 12 hours. The NHS suggests small amounts more often than usual.
- Give formula in small amounts often. If your baby isn't keeping fluids down, the RCH suggests switching to oral rehydration solution for 12 hours, then going back to formula in small amounts regularly.
- Keep formula at normal strength. The NHS says not to make formula weaker, and the RCH says not to dilute it.
- Offer a drink every time your baby vomits. The RCH says children still absorb much of what they drink, even with vomiting or diarrhoea.
- Ask a pharmacist about oral rehydration solution. The NHS suggests asking a pharmacist to recommend one. The RCH notes many children dislike the salty taste.
- For babies 6 to 12 months who aren't feeding normally, the RCH suggests giving about 5 mL by syringe (no needle) every 5 minutes while awake, for 4 hours. See a doctor if there's no improvement or your baby can't keep anything down.
Skip lemonade, ginger ale and sports drinks. The RCH says they're high in sugar and can make dehydration worse. It also says not to give medicines to slow diarrhoea, because of their side effects.
Water for young babies. The RCH says babies under 6 months get their fluids from breast milk or formula and don't need water. The NHS suggests small sips of extra water for babies on formula or solids, boiled and cooled first for babies under 6 months. Ask your doctor before giving water to a young baby who is unwell, and see water for babies.
When should I get help for a dehydrated baby?
Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) now if your baby:
- has signs of dehydration and is struggling to breathe, or has blue or grey skin
- is floppy, very drowsy, hard to wake or can't be woken
- has had no wet nappy or wee for 12 hours
- is under 3 months and has a temperature of 38°C (100.4°F) or more
- has green vomit (see when to call the doctor)
Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) or go straight to emergency for severe signs such as sunken eyes or a sunken soft spot, cold hands, mottled skin or unusual sleepiness. The RCH says these need hospital care. If your baby is alert and breathing normally and you can get there quickly, going straight to the nearest emergency department is fine.
Get medical help today from a same-day GP, an after-hours doctor or a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US) if:
- your baby is under 6 months and has any sign of dehydration
- there are fewer wet nappies, darker wee, a dry mouth or fewer tears
- your baby is under 6 months and vomiting (for any fever under 3 months, use the emergency tier above)
- your baby can't keep fluids down, or isn't improving after extra fluids
- symptoms haven't gone after 24 hours
- your baby has a long-term heart, kidney or gut condition
Talk to your GP or child-health nurse at your next visit if your baby had a mild bout that settled and you'd like a plan for next time, such as which rehydration solution to keep at home.
If a sign gets worse, move up a tier. If you're unsure which tier fits, call a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US) for advice.
What's useful to write down?
Note the last feed you know about, wet nappies with rough times, and when any vomiting or diarrhoea started. Be clear about gaps: "the morning wasn't written down" is different from "there was no wee this morning". That difference helps a doctor, but never wait to fill a gap before getting help.
