Table 1.

Classification of hyponatremia according to time-to-onset and symptom severity (7).

Criteria	Values
Biochemical severity*
Mild	130–135
Moderate	125–130
Profound	<125
Time-to-onset, hours
Acute	<48
Chronic	≥48
Severity of clinical presentation†
Moderately severe	Headache, confusion, nausea
Severe	Emesis, cardiorespiratory distress, somnolence/coma (GCS ≤ 8), seizures

*Measured as serum sodium (mEq/L); ^†symptoms presented.