See also

Gastroenteritis 
Intravenous fluids 
Maintenance fluids calculator 
Nasogastric fluids 
Resuscitation: Care of the seriously unwell child

Key points

1. Serial weights are the best measure of acute changes in fluid status. Clinical signs can help estimate the severity of dehydration but are often imprecise
2. If a child is haemodynamically unstable (ie in shock), prompt fluid resuscitation with intravenous fluid boluses must be given. Sepsis must be considered
3. Rehydrate enterally (orally or nasogastric route), unless severe dehydration or shock

Background

Dehydration can occur with many childhood illnesses, and results from

• Increased fluid loss
  • Gastrointestinal ie vomiting and diarrhoea
  • Renal eg diabetic ketoacidosis
  • Cutaneous eg excessive sweating, burns
  • Third space losses eg sepsis, bowel obstruction
• Decreased fluid intake

The mainstay of treatment is fluid management, determined by a combination of the degree of dehydration, maintenance fluid requirements and any ongoing losses

Assessment

The most accurate assessment of degree of dehydration is based on the difference between the pre-morbid body weight (within last 2 weeks) and current body weight (eg a 10 kg child who now weighs 9.5 kg has a 500 mL water deficit and is 5% dehydrated)

When a recent weight is not available, use the history and clinical examination to estimate the degree of dehydration

History

• Intake: food and fluid intake in comparison to normal
• Output: urine and stool in comparison to normal
• Excessive losses, eg vomiting, frequent urination or diarrhoea
• Recent use of potentially hypertonic/hypotonic fluids, eg diluted formula or soft drinks, water only, fortified feeds
• Risk factors for severe dehydration and electrolyte disturbances
  • Infants <6 months old
  • Gastrointestinal pathology (eg short gut syndrome, ileostomy, colostomy, Hirschsprung disease)
  • Cystic fibrosis
  • Renal impairment
  • Use of diuretics
  • Metabolic disorders
• Conditions where dehydration carries a high risk for children
  • Complex/cyanotic congenital heart disease (especially cardiac shunts)
  • Slow weight gain
  • Post organ transplant
  • Use of nephrotoxic medications

Examination

• Vital signs
• Weight
• Assess hydration level based on a combination of signs (see table below)
  • Children with mild dehydration have no clinical signs. They may have increased thirst and/or reduced urine output
  • More numerous/pronounced signs indicate greater severity
  • For clinical shock, one or more of these signs will be present: reduced conscious state, tachycardia, tachypnoea, hypotension, weak peripheral pulses, mottled/cold peripheries, acidosis
  • If in doubt, manage as per severe dehydration

Assessment of severity

Management

Investigations

If only mild to moderate dehydration is present and there is a clear explanation for dehydration (eg viral illness, reduced oral intake), investigations are not usually necessary

Check electrolytes and blood glucose level (BGL) in children with

• age <6 months with poor feeding or large volume losses
• intravenous fluid requirements
• severe dehydration
• clinical signs of electrolyte disturbances eg hypertonia, hyperreflexia, convulsions, jittery movements, altered conscious state, irregular heart rate, doughy skin turgor (sign of hypernatremia)
• pre-existing medical conditions that predispose to electrolyte abnormalities (eg renal impairment, cystic fibrosis, metabolic disorders, diuretic use)
• history of hyper or hypotonic fluid administration

Treatment

• For children with mild or moderate dehydration, enteral (oral or NG) rehydration is preferable. For suggested rates for enteral rehydration see Nasogastric fluids
• IV fluid rehydration is required in severe dehydration or children who cannot tolerate enteral rehydration. For detailed advice regarding fluid prescription including suggested rates for rehydration, see Intravenous fluids
• Replacement of fluids may be rapid in most cases of gastroenteritis but should be slower in other illnesses (eg respiratory infection, diabetic ketoacidosis, meningitis and electrolyte disturbances including hypernatremia)

Approach to rehydration

Consider consultation with local paediatric team when

• Child presents with shock
• Child has electrolyte disturbance and/or predisposing factors for severe or complicated dehydration

Consider transfer when

• Clinical signs of shock persist after maximum of 40 mL/kg fluid given in boluses. Consider other possible causes of shock (eg sepsis and need for antibiotics) other than dehydration alone
• Severe electrolyte derangement

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval services

Consider discharge when

• Children with mild dehydration and no serious underlying cause can be discharged with advice on continuing rehydration at home
• Consider a review within 48 hours for young infants

Parent information

Kids health info - dehydration

Additional notes

• Neonatal intravenous fluid requirements
• Hyponatraemia
• Hypernatraemia

Last updated April 2026