Normal Sodium Level for a 3-Year-Old
For a healthy 3-year-old child, the normal serum sodium level is 135-145 mmol/L, which is the same reference range used for adults and older children. 1
Serum Sodium Reference Range
The standard reference range for serum sodium concentration is 135-145 mmol/L across all age groups, including 3-year-old children. 1, 2 This range applies to both inpatient and outpatient settings, though hospitalized children may have slightly lower values on average. 3
Classification of Sodium Abnormalities
- Normal sodium: 135-145 mmol/L 1
- Mild hyponatremia: 130-134 mmol/L 2, 4
- Moderate hyponatremia: 120-129 mmol/L 2
- Severe hyponatremia: <120 mmol/L 2, 4
- Hypernatremia: >145 mmol/L 5
Dietary Sodium Intake Recommendations
While serum sodium levels remain constant, dietary sodium intake recommendations vary by age. For a 3-year-old child:
- Adequate Intake (AI): 1,000 mg/day (approximately 43 mmol/day) 1
- Upper Limit: 1,500 mg/day (65 mmol/day) 1
Important Context on Actual Intake
The average 3-year-old in the United States consumes significantly more sodium than recommended. In national surveys, 77% of children aged 1-3 years exceeded the recommended upper limit, with a mean intake of 1,918 mg/day. 1 This excess intake primarily comes from processed foods (75% of total sodium), not from salt added at the table. 1
Clinical Considerations
When to Check Sodium Levels
Sodium determination is advised on admission for children with:
- Bronchiolitis 4
- Pneumonia 4
- Pulmonary exacerbations of cystic fibrosis 4
- Acute respiratory infections 4
Symptoms by Severity
- Mild hyponatremia (130-134 mmol/L): Usually asymptomatic or minimal symptoms 2, 4
- Moderate hyponatremia (120-129 mmol/L): Lack of concentration, nausea, forgetfulness, apathy, loss of balance 2
- Severe hyponatremia (<120 mmol/L): Coma, seizures, cerebral edema 2, 4
Special Populations
Children with chronic kidney disease may require individualized sodium management, with supplementation needed for salt-wasting conditions (polyuric renal dysplasia, obstructive uropathy) or restriction needed for hypertension. 1