The normal range of serum sodium in the human body is -

Correct option is A

Ans. (a) 135-145 mEq/L
Explanation:
Sodium (Na⁺) is a major extracellular electrolyte essential for:
· Maintaining fluid balance and osmotic pressure
· Nerve impulse transmission
· Muscle contraction
· Regulation of blood pressure
Normal Serum Sodium Range:
✅ 135-145 mEq/L (milliequivalents per liter)
Sodium Imbalances:
1. Hyponatremia (< 135 mEq/L)
· Causes: Excess water intake, SIADH (Syndrome of Inappropriate Antidiuretic Hormone), kidney disease, heart failure.
· Symptoms: Confusion, seizures, muscle cramps, weakness.
2. Hypernatremia (> 145 mEq/L)
· Causes: Dehydration, excessive sodium intake, diabetes insipidus.
· Symptoms: Thirst, confusion, restlessness, seizures.
Why are the other options incorrect?
1. 3.6-5.0 mEq/L → (Incorrect Choice)
· This is the normal range for serum potassium (K⁺), not sodium.
2. 95-107 mEq/L → (Incorrect Choice)
· This is the normal range for serum chloride (Cl⁻), not sodium.
3. 21-29 mEq/L → (Incorrect Choice)
· This is the normal range for serum bicarbonate (HCO₃⁻), not sodium.