Dehydration in Kids: Signs, Fluids by Age, and When to Call
Less urine, a dry mouth, and fewer tears can signal dehydration when a child has vomiting or diarrhea. If your child is alert and swallowing normally, offer small, frequent amounts of age-appropriate fluids. Babies under 6 months need prompt advice from their pediatrician about repeated vomiting or diarrhea. For any age, contact the pediatrician right away if dehydration signs appear or your child cannot keep fluids down. Call 911 if your child is unresponsive, hard to wake, or struggling to breathe.
Signs to watch for
Compare your child's behavior and urine output with their usual pattern. Look for:
Fewer wet diapers or less frequent urination.
A dry mouth or fewer tears when crying.
Less play, unusual tiredness, or irritability.
Dizziness when standing in a child old enough to describe it.
A sunken soft spot in a baby whose soft spot is still open.
The American Academy of Pediatrics lists these and more severe warning signs in its guide to dehydration in infants and children. Do not wait for every sign to appear. Dehydration can happen without a fever, and urine color alone cannot tell you how serious it is.
Which fluids to offer by age
An oral rehydration solution, or ORS, contains water, sugar, and salts in a balance designed to replace fluid losses. Choose a commercial product intended for oral rehydration and prepare it exactly as directed. Do not add extra water or powder.
Babies under 6 months
Contact the pediatrician promptly for repeated vomiting or diarrhea; younger babies can lose fluid quickly. Continue breast milk or correctly mixed formula as tolerated while getting advice. Do not replace feeds with plain water or dilute formula. Ask the clinician whether ORS is needed and how to give it.
Babies 6 months to their first birthday
Offer breast milk or undiluted formula in smaller, more frequent feeds. If these are not tolerated, a commercial ORS may be used. Contact the pediatrician if vomiting continues, intake remains low, or wet diapers decrease. Do not use plain water as the replacement fluid for vomiting or diarrhea.
Children 1 year and older
Offer small, frequent sips of commercial ORS, especially with repeated vomiting or watery diarrhea. Plain water alone does not replace the salts lost with substantial vomiting or diarrhea. Avoid relying on soda, full-strength juice, or sports drinks for rehydration; their sugar and salt balance differs from ORS, and very sugary drinks can worsen diarrhea.
The AAP's age-specific guidance on drinks during vomiting explains fluid choices and when to contact the pediatrician.
Help fluids stay down
Start with small sips or spoonfuls every few minutes instead of a large drink at once.
If your child vomits again, pause briefly and restart more slowly with smaller amounts.
Keep your child upright and supervised while drinking. Do not force fluids or give anything by mouth if your child is not fully alert or cannot swallow safely.
Continue breastfeeding. Offer usual age-appropriate foods as tolerated once vomiting eases; do not force food.
Keep track of drinking, vomiting, diarrhea, wet diapers or bathroom trips, and changes in alertness.
If even small amounts keep coming back up, contact the pediatrician right away rather than repeatedly trying larger drinks.
When to get medical help
Contact the pediatrician right away for reduced urination, a dry mouth, fewer tears, unusual tiredness, dizziness, inability to drink, repeated vomiting of fluids, or blood in the stool. A baby under 6 months with repeated vomiting or diarrhea also needs prompt advice. If the office is closed, use its after-hours service; if timely advice is unavailable, seek urgent medical assessment.
Go to an emergency department now for signs of severe dehydration, such as very little urine together with marked sleepiness, sunken eyes, or cool, discolored hands and feet. Green or bloody vomit or severe abdominal pain also needs emergency assessment. Do not delay care to finish a home rehydration attempt.
Call 911 if your child is unresponsive, hard to wake, has trouble breathing, or has blue or gray lips. Do not give fluids by mouth while waiting if your child is not fully alert or cannot swallow safely.
For a closely related situation, see our question about a baby who keeps vomiting and seems lethargic without a fever. If your concern is recovery after an earlier illness, see the separate question about whether IV fluids are needed after a past fever and possible dehydration. A clinician decides whether oral fluids are enough or another treatment is needed based on your child's current condition.
This article provides general education and does not replace individualized medical advice from your child's healthcare professional.
By Sang Hyun Ahn, MD
