Which electrolyte imbalance is characterized by a serum sodium level less than 135 mEq/L?

A Hypernatremia
B Hyponatremia ✓
C Hyperkalemia
D Hypokalemia

Explanation

Hyponatremia is an electrolyte imbalance characterized by a serum sodium level less than 135 mEq/L, often due to excessive water intake or sodium loss.

Mnemonic

Low Na = Hyponatremia

Source

Harrison's Principles of Internal Medicine
Electrolytes and Acid-Base Balance Electrolytes Sodium Imbalance Easy MEDICAL Confidence: high