Child dehydration: Early signs to watch for

Child Dehydration | Image Credit: © Sergey Chayko - stock.adobe.com.

Proper hydration is a foundational—but often underemphasized—aspect of pediatric recovery. Whether a child is bouncing back from a febrile illness, a gastrointestinal virus, or even a mild respiratory infection, maintaining fluid balance is critical in avoiding complications and supporting recovery.

Children are particularly vulnerable to fluid shifts, and the signs of dehydration may not always be obvious until the condition becomes more advanced. As pediatricians, we can help bridge that gap by recognizing the early signs of dehydration, guiding appropriate rehydration strategies, and helping families understand when it’s time to seek further care.

How illness changes a child’s hydration needs

Acute illness often disrupts the balance between fluid intake and loss. Fever increases insensible losses through sweating and a faster respiratory rate. Vomiting and diarrhea, common in viral gastroenteritis, can rapidly deplete both fluids and electrolytes. Even mild illnesses can suppress appetite and reduce fluid intake, particularly in younger children.

Infants and toddlers are especially at risk. Their smaller size, higher metabolic rate, and greater body water percentage mean they lose fluids more quickly. And because they depend entirely on caregivers for hydration, any disruption in feeding—whether due to fatigue, fussiness, or gastrointestinal (GI) symptoms—can escalate into a clinical issue within hours.

Add to that the fact that intestinal inflammation can impair fluid and electrolyte absorption, and it becomes clear why oral rehydration therapy (ORT) is a key part of management. The sodium-glucose cotransport mechanism remains functional even during episodes of diarrhea, which is why balanced oral rehydration solutions (ORS) remain the gold standard for mild to moderate dehydration.¹

Recognizing dehydration: What to look for

In many cases, dehydration isn’t immediately obvious, especially to caregivers. The signs often evolve gradually, and younger children may not clearly express thirst or discomfort.

Early signs to watch for include:

• Dry lips or mouth
• Decreased urine output (fewer wet diapers, less frequent bathroom trips)
• Irritability or low energy
• Reduced tear production

More concerning signs that suggest moderate to severe dehydration:

• Sunken eyes or fontanelle (in infants)
• Cool extremities
• Delayed capillary refill
• Tachycardia
• Lethargy or altered responsiveness
• Minimal or no urine output over 8 hours
  

A few key questions during a sick visit can go a long way:
 “How often has your child urinated today?”
 “Are they drinking fluids voluntarily?”
 “Any vomiting or diarrhea?”

Combining that caregiver history with a focused physical exam—checking skin turgor, perfusion, and mucosal hydration—can help identify children who may be on the cusp of more significant fluid loss.

Rehydration at home: What to recommend

Oral rehydration remains the mainstay of treatment for mild to moderate dehydration. ORS is both effective and safe when administered correctly, and its use is supported by guidelines from the World Health Organization and American Academy of Pediatrics.³ Luckily, there are several formulations now available that taste good, do not have added artificial colors, sweeteners, and extra sugar, and are also covered by HSA/FSA benefits.

For most cases of mild to moderate dehydration, ORT is safe, effective, and simple to administer at home. The goal is to replace fluid losses slowly and consistently, even in the presence of ongoing symptoms.

Helpful guidance for families includes:

• Offer small amounts of fluid frequently—5 to 10 mL every few minutes is a good starting point
• Use a spoon or oral syringe for younger children who won’t drink from a cup
• Continue breastfeeding or formula feeding in infants; no need to interrupt unless the child is vomiting persistently
• Avoid sugary drinks and sodas, which can worsen diarrhea or lead to further electrolyte imbalance

For kids resistant to standard ORS, flavored or chilled options may improve compliance. Importantly, hydration should remain a focus for at least 24–48 hours after symptoms resolve. Recovery isn’t just about symptom resolution—it’s about restoring normal energy levels, gut function, and perfusion.

When to escalate care

Not all cases can be managed at home. Parents should know what signs mean it’s time to call the pediatrician or head to urgent care.

Escalation is warranted when:

• A child can’t keep fluids down for more than a few hours
• There’s no urine output for 8 hours or more
• The child is increasingly lethargic or difficult to arouse
• Breathing or heart rate becomes rapid
• There’s concern for a sunken fontanelle or poor perfusion
• Home hydration attempts aren’t improving symptoms

In these situations, IV fluids and further clinical assessment are often necessary to correct deficits and monitor for underlying complications, such as electrolyte disturbances or acute kidney injury.

Hydration is not a secondary concern—it’s central to the healing process. As pediatricians, we can support families by helping them recognize early warning signs, offering clear guidance on oral rehydration, and ensuring they know when more advanced care is needed.

By making hydration a routine part of our clinical conversations—especially during sick visits and follow-ups—we can help reduce the risk of complications and improve outcomes for children recovering from illness.

About the authors:

Dr. Tanya Altmann is a UCLA-trained pediatrician and working mom. A nationally recognized child health expert, she has 25 years of experience caring for children. She is the author of several best-selling parenting books, including the American Academy of Pediatrics 'What to Feed Your Baby,' and is Editor-in-Chief of 'Caring for Your Newborn and Young Child: Birth to Age 5 and Your Baby’s First Year'. As a regular child health expert for numerous news programs and talk shows, Dr. Tanya communicates complicated medical issues into easily understood concepts, discusses breaking medical news stories, and tackles controversial parenting issues. She started Calabasas Pediatric Wellness Center to provide personalized and integrative comprehensive pediatric healthcare, and is also a member of Cure Hydration's medical advisory board.

Dr. Marina Salama is a pediatrician with over 10 years of experience treating infants, children, and teenagers. Her experience spans a range of pediatric settings, including private practice, community clinics, hospital medicine, and house calls, ensuring that she offers comprehensive, compassionate care to her patients and families. She earned her medical degree from The George Washington University and completed her pediatric residency atthe University of California, Los Angeles. Throughout her career, Dr. Marina has been passionate about providing up-to-date, high-quality, personalized care to children and supporting families through their health and wellness journeys. She lives in Encino with her husband and their three children.

References

1. Centers for Disease Control and Prevention. Managing Acute Gastroenteritis Among Children: Oral Rehydration, Maintenance, and Nutritional Therapy. MMWR Recomm Rep. November 21, 2003. Accessed April 11, 2025. https://www.cdc.gov/mmwr/pdf/rr/rr5216.pdf
2. King CK, Glass R, Bresee JS, Duggan C; Centers for Disease Control and Prevention. Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy. MMWR Recomm Rep. 2003;52(RR-16):1-16.
3. Feld LG, Neuspiel DR, Foster BA, et al. Clinical Practice Guideline: Maintenance Intravenous Fluids in Children. Pediatrics. 2018;142(6):e20183083. doi:10.1542/peds.2018-3083
4. World Health Organization. Oral Rehydration Salts: Production of the New ORS. WHO. January 1, 2006. Accessed April 11, 2025. https://www.who.int/publications/i/item/WHO-FCH-CAH-06.1