A nurse is feeding a client who is on a diuretic. Upon wiping the patient's cheek, she notices facial twitching. She notices the twitching occurs upon every tap. This may be a sign of what electrolyte imbalance?

Choice A reason: Hypokalemia can cause muscle weakness, cramps, and cardiac arrhythmias, but it does not typically present with facial twitching or Chvostek’s sign. It affects skeletal and cardiac muscle function more broadly. Choice B reason: Hypophosphatemia may lead to muscle weakness and neurological symptoms, but facial twitching is not a classic presentation. It is more associated with respiratory muscle fatigue and altered mental status. Choice C reason: Hypocalcemia is characterized by neuromuscular excitability, and facial twitching upon tapping the cheek is known as Chvostek’s sign—a classic indicator of low calcium levels. Diuretics, especially loop diuretics, can cause calcium loss, making this a relevant clinical finding. Choice D reason: Hyponatremia can cause confusion, seizures, and lethargy, but it does not typically cause facial twitching or Chvostek’s sign. Its neurological symptoms are more diffuse and related to cerebral edema.