Signs of Dehydration in Children

Your child has been vomiting, has diarrhea, or has a fever and is barely touching their drink. Sooner or later the same question arrives: how would you know if they were becoming dehydrated?

Part of the answer depends on age. Some warning signs belong to babies specifically. Others are easier to notice in a child old enough to tell you how they feel.

What follows is what American Academy of Pediatrics guidance sets out for parents — and, just as importantly, what it does not ask you to do at home.

Why Children Dehydrate Faster Than Adults

Dehydration happens when more fluid leaves the body than goes into it.

Young children are more vulnerable than older children and adults for two reasons the AAP sets out plainly. Their bodies are less efficient at conserving water. And because they are small, it takes less fluid loss to matter.

That combination is why an illness an adult might shrug off can leave a young child in a different situation.

Signs of Dehydration in Babies

A baby cannot tell you they are thirsty, so the useful signals are changes to their normal pattern.

• Fewer wet diapers. For infants, the AAP identifies fewer than six wet diapers in a day as a warning sign.
• A sunken soft spot. A sunken fontanelle can be a sign in an infant or young toddler. This one is specific to babies — once the soft spot has closed, it is no longer something to check.
• Fewer tears when crying.
• A dry, parched mouth.
• Passing urine less often than usual.

If a breastfed baby develops diarrhea, breastfeeding can generally continue. The AAP notes that many breastfed babies can stay hydrated with continued feeding, with electrolyte solution added only if the doctor advises it. Exclusively breastfed babies are also less likely to develop severe diarrhea.

Signs of Dehydration in Young Children

The AAP’s detailed list for this age group covers changes you can see at home:

• Playing less than usual
• Passing urine less often than usual
• A dry or parched mouth and tongue
• Fewer tears when crying, and dry eyes
• Unusual fussiness, or unusual sleepiness
• Sunken eyes
• Wrinkled skin
• Cool or discoloured hands and feet
• Passing urine only once or twice in a day

The AAP groups the last four differently from the first. They sit with more serious fluid loss. That grouping is there to help parents recognise when to act, not to create a scoring system for use at home.

One detail most guides leave out: the stool pattern

What is happening in the diaper can depend on what caused the fluid loss.

When diarrhea is the cause, stools stay loose. When the loss is coming from vomiting or from a child simply not drinking, bowel movements tend to become less frequent instead.

It is worth knowing because a parent watching only for diarrhea can miss dehydration that arrived through another route.

Signs of Dehydration in Older Children

An older child can describe what they are feeling, which adds signals a baby cannot give you.

• Weakness or dizziness on standing. AAP symptom guidance notes that a child with severe dehydration can become too weak to stand and may be very dizzy when trying.
• Darker yellow urine alongside passing less of it. AAP symptom guidance lists darker urine together with reduced urine output as an early sign.
• A dry mouth, dry eyes, and fewer tears. These signs can also appear in older children.

How Vomiting, Diarrhea and Fever Fit Together

Vomiting makes dehydration more likely on its own. The AAP notes that the risk climbs further when fever is making a child sweat more, or when diarrhea is adding a second route of fluid loss.

Depending on how severe or prolonged the vomiting is, a child can also lose sodium, potassium and chloride — which is why plain fluid is not always the right replacement.

If fever is part of what is going on, our guide to fever in children covers the age-based thresholds and warning signs that apply to the temperature itself.

And if vomiting and diarrhea are what started all this, our guide to child vomiting and diarrhea covers what AAP guidance says about food, medicines and when to call.

What Parents Can Do at Home

The AAP describes oral rehydration as an effective and safe way to prevent dehydration at home.

When a child is vomiting, small amounts offered frequently tend to work better than a full drink. Liquids are also less likely than solid food to set off more vomiting. If your child cannot manage a cup, a medicine cup, syringe or teaspoon can be used.

Babies 6 to 12 months

Breast milk or formula stays the main fluid. If it is not being tolerated, the AAP points to a commercial rehydration solution containing sugars and salts.

Plain water is not the answer at this age. This is an important distinction in AAP guidance.

Children 1 year and older

Commercial oral rehydration solutions, including the popsicle form, are listed as options. So are apple juice or a sports drink diluted with an equal amount of water.

Two things matter about that second option. The dilution is not a detail — it is the condition under which those drinks are listed at all. And they are not interchangeable with an oral rehydration solution: sports drinks do replace salts, but they can carry enough sugar to make diarrhea worse.

Food, and what recovery looks like

Food does not need to be withheld beyond about 24 hours. A child needs normal nutrition to start regaining strength.

Once eating resumes, stools may stay loose for a while. The AAP is clear that this does not necessarily mean things are going badly. What tells you your child is turning the corner is different:

• More activity
• A better appetite
• Passing urine more often
• The dehydration signs fading

Two smaller notes. Milk sometimes makes diarrhea worse, so in a child over one your pediatrician may suggest pausing it or switching to lactose-free for a period — that is their call, not a general rule. And too much juice or sweetened drink can itself produce ongoing loose stools, without affecting appetite, growth or hydration.

When to Call Your Pediatrician

The AAP says to call your child’s doctor right away if your child is too sick to drink, becomes lethargic, or is showing signs of dehydration.

You do not need to wait for several signs to line up. A concerning change can be enough to seek medical advice.

The Situation the AAP Treats as an Emergency

There is one combination worth knowing precisely because the AAP’s current guidance on choosing between a pediatrician, urgent care and the emergency room places it in the emergency-room category.

That is not a judgement call being handed to you. It is where the AAP guidance places that specific picture.

Severe dehydration can require admission to hospital so that fluids can be given intravenously. Milder cases may need only an electrolyte solution, given according to your pediatrician’s directions.

A Simple Check

• Drinking. Is your child taking fluids, and keeping them down?
• Urine. How often, compared with their normal? What colour?
• Mouth and tears. Dry mouth? Fewer tears than you would expect?
• Behaviour. Alert and interacting, or unusually sleepy, fussy, weak or dizzy?
• Direction. Better than earlier, the same, or worse?

This does not tell you how dehydrated your child is. It gives you a consistent way to notice change — and change is the thing worth acting on.

If the Question Is Really About School

Managing fluid loss at home and deciding whether to send a child in are two different questions. For the second, see our guide to when to keep your child home from school.

The Bottom Line

Dehydration does not always announce itself with one dramatic symptom.

In babies, watch the diapers, the tears, the mouth and the soft spot. In young children, watch play, urine, and how they look. In older children, ask them how they feel — and pay attention if they are weak or dizzy when standing.

And keep the two jobs separate. Yours is to notice changes and keep appropriate fluids going. Grading how serious dehydration is belongs to your child’s healthcare provider.

Sources

• American Academy of Pediatrics / HealthyChildren.org — Signs of Dehydration in Infants & Children. Updated 24 September 2019.
• American Academy of Pediatrics / HealthyChildren.org — Treating Dehydration with Electrolyte Solution. Updated 6 February 2023.
• American Academy of Pediatrics Section on Gastroenterology, Hepatology & Nutrition / HealthyChildren.org — Drinks to Prevent Dehydration When Your Child is Vomiting. Updated 7 February 2023.
• HealthyChildren.org Symptom Checker (Schmitt Pediatric Guidelines) — Vomiting With Diarrhea.
• HealthyChildren.org Symptom Checker (Schmitt Pediatric Guidelines) — Diarrhea.
• HealthyChildren.org Symptom Checker (Schmitt Pediatric Guidelines) — Drinking Fluids – Decreased.
• American Academy of Pediatrics / HealthyChildren.org — Urgent Care, ER or Pediatrician? A Parent Guide. Updated 14 May 2026.