What are the signs of dehydration in a 21-month-old and how is it treated?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: June 9, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

Dehydration in a 21-month-old can be identified by signs such as decreased wet diapers, dry mouth or tongue, absence of tears when crying, sunken eyes or fontanelle, irritability, lethargy, and decreased activity, and should be treated with oral rehydration solutions like Pedialyte for mild to moderate cases, and IV fluids for severe cases, as recommended by the 2017 Infectious Diseases Society of America clinical practice guidelines 1. The signs of dehydration in a 21-month-old include:

  • Decreased wet diapers (fewer than 4-6 in 24 hours)
  • Dry mouth or tongue
  • Absence of tears when crying
  • Sunken eyes or fontanelle (soft spot)
  • Irritability
  • Lethargy
  • Decreased activity Treatment primarily involves fluid replacement, with the following approaches:
  • For mild dehydration, offer frequent small amounts of oral rehydration solutions like Pedialyte (5-15 ml every 5-15 minutes), gradually increasing as tolerated, as recommended by the 2017 IDSA guidelines 1.
  • Continue breastfeeding or formula if the child can keep it down.
  • Avoid plain water, juice, or soda as these lack proper electrolytes.
  • For moderate dehydration, maintain the same approach but more aggressively.
  • Severe dehydration requires immediate medical attention as IV fluids may be necessary, with boluses of Ringer's lactate solution, normal saline, or a similar solution administered until pulse, perfusion, and mental status return to normal 1. After rehydration, gradually reintroduce normal diet within 24 hours. It is essential to monitor the child's hydration status frequently to assess the adequacy of replacement therapy and to seek medical care immediately if the child refuses fluids, shows signs of severe dehydration, or symptoms worsen, as dehydration in toddlers can be dangerous due to their higher metabolic rates and proportionally greater body water content, making them vulnerable to rapid fluid loss, particularly during illnesses with vomiting, diarrhea, or fever 1.

From the Research

Signs of Dehydration in a 21-Month-Old

  • Dry mouth and throat
  • Few or no tears when crying
  • Decreased urine output or dark yellow urine
  • Sunken eyes
  • Decreased skin elasticity
  • Irritability or restlessness
  • Lethargy or lack of energy

Treatment of Dehydration

  • Oral rehydration is the preferred method of treatment for mild to moderate dehydration, as stated in 2 and 3
  • Oral rehydration solutions (ORS) such as those recommended by the World Health Organization can be used to treat dehydration, as discussed in 4 and 3
  • Intravenous fluids may be necessary for severe dehydration or if the child is unable to take oral fluids, as mentioned in 2 and 5
  • Subcutaneous infusion of fluids (hypodermoclysis) can also be used to treat mild to moderate dehydration, as noted in 6

Prevention of Dehydration

  • Encourage the child to drink plenty of fluids, such as oral rehydration solutions or breast milk/formula
  • Offer small, frequent feedings to help prevent dehydration, as suggested in 4
  • Monitor the child's urine output and stool frequency to detect early signs of dehydration
  • Educate caregivers on the importance of preventing dehydration and recognizing its signs and symptoms, as emphasized in 6

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Evaluation and Management of Dehydration in Children.

Emergency medicine clinics of North America, 2018

Research

Principles and Practice of Oral Rehydration.

Current gastroenterology reports, 2019

Research

Understanding body fluid balance, dehydration and intravenous fluid therapy.

Emergency nurse : the journal of the RCN Accident and Emergency Nursing Association, 2025

Research

Understanding clinical dehydration and its treatment.

Journal of the American Medical Directors Association, 2008

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.