What Is Sodium in a Blood Test?

Sodium is the primary electrolyte regulating fluid balance, nerve impulses, and blood pressure.

Normal Range

• 135–145 mEq/L
• Hyponatremia: below 135
• Hypernatremia: above 145
• Severe hyponatremia: below 125 — brain swelling risk

Low Sodium Causes

• Excessive water intake
• Heart failure
• Liver cirrhosis
• SIADH
• Diuretics
• Hypothyroidism
• Adrenal insufficiency

High Sodium Causes

• Dehydration — most common
• Diabetes insipidus
• Excessive salt intake

Symptoms

• Low: headache, confusion, nausea, seizures
• High: thirst, confusion, muscle twitching
• Rapid sodium correction can be dangerous — correct slowly under medical supervision