Electrolyte Imbalances Practice Questions
20 free Electrolyte Imbalances practice questions for the NCLEX Exam. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What electrolyte imbalance is most likely in a patient with serum sodium 152 mEq/L, dry mucous membranes, and restlessness?
- A Hyponatremia
- B Hypernatremia
- C Hypokalemia
- D Hypermagnesemia
Correct answer: Hypernatremia
A sodium level above 145 mEq/L defines hypernatremia, and the signs of dry mucous membranes and neuro restlessness align with fluid shift/out-of-cellular dehydration.
Which ECG change is most likely in a patient with serum potassium of 6.2 mEq/L?
- A U waves
- B Flattened T waves
- C Peaked T waves
- D Wide QRS and absent P waves
Correct answer: Peaked T waves
Hyperkalemia typically causes peaked (tented) T waves early, with progression to wide QRS if severe; U waves and flattened T waves are more hypokalemia.
Which imbalance is present in a patient with chronic kidney disease with a total serum calcium of 7.8 mg/dL and complaining of numbness and tingling around the mouth?
- A Hypercalcemia
- B Hypocalcemia
- C Hypermagnesemia
- D Hyponatremia
Correct answer: Hypocalcemia
A calcium below ~8.4–9.0 mg/dL indicates hypocalcemia; the neuromuscular irritability (perioral numbness/tingling) is classic for hypocalcemia.
A patient receiving IV magnesium sulfate post-pre-eclampsia develops decreased deep tendon reflexes, hypotension, and bradycardia. Which electrolyte imbalance is likely?
- A Hypomagnesemia
- B Hypermagnesemia
- C Hypokalemia
- D Hypernatremia
Correct answer: Hypermagnesemia
Elevated magnesium above normal (~2.1 mg/dL) causes depressed neuromuscular/junction activity: decreased reflexes, hypotension, bradycardia.
Which of the following is least likely to lead to hypokalemia?
- A Loop diuretic therapy
- B Vomiting
- C Potassium-sparing diuretic (e.g., spironolactone) use
- D Excessive insulin administration
Correct answer: Potassium-sparing diuretic (e.g., spironolactone) use
Potassium-sparing diuretics reduce potassium loss, so they are not likely to cause hypokalemia; the other options do.
A patient with sodium of 128 mEq/L, confusion, and a seizure needs immediate nursing action. What is the best action?
- A Infuse hypotonic saline
- B Restrict fluid and monitor
- C Administer hypertonic saline cautiously
- D Give oral sodium tablets only
Correct answer: Administer hypertonic saline cautiously
Severe hyponatremia (below 135 mEq/L) with neurologic changes/seizure may require hypertonic saline infusion under supervision to raise sodium safely.
Which lab value falls within the normal range?
- A Potassium 5.6 mEq/L
- B Sodium 131 mEq/L
- C Calcium 9.2 mg/dL
- D Magnesium 2.4 mg/dL
Correct answer: Calcium 9.2 mg/dL
Normal sodium ~135–145 mEq/L, potassium ~3.5–5.1 mEq/L, calcium ~8.4–10.6 mg/dL, magnesium ~1.3–2.1 mg/dL. Thus only calcium 9.2 mg/dL is within normal.
What sign is most indicative of hypomagnesemia?
- A Loss of deep tendon reflexes
- B Muscle twitching and tetany
- C Bradycardia
- D Hypercalcemia
Correct answer: Muscle twitching and tetany
Low magnesium often causes neuromuscular excitability: twitching, positive Trousseau/Chvostek signs, tetany; loss of reflexes is hypermagnesemia.
A patient with hypercalcemia is at greatest risk for which complication?
- A Tetany
- B Cardiac dysrhythmias
- C Seizures
- D Muscle cramps and spasms
Correct answer: Cardiac dysrhythmias
Hypercalcemia increases the threshold for nerve/muscle excitability and can lead to cardiac arrhythmias and shortened QT; tetany/cramps are more hypocalcemia.
A patient on adrenal insufficiency has hyperkalemia (6.0 mEq/L) with peaked T-waves. Which initial treatment may be given emergently?
- A Oral potassium supplement
- B IV calcium gluconate
- C IV hypotonic saline
- D Loop diuretic alone
Correct answer: IV calcium gluconate
In severe hyperkalemia with ECG changes calcium gluconate stabilizes cardiac membranes before other treatments.
Which electrolyte imbalance may result from prolonged nasogastric suctioning and diarrhea?
- A Hypermagnesemia
- B Hypernatremia
- C Hypokalemia
- D Hypercalcemia
Correct answer: Hypokalemia
Prolonged GI losses of fluid and electrolytes commonly cause potassium loss → hypokalemia; suctioning/diarrhea do not typically cause hypermagnesemia or hypercalcemia.
A patient with SIADH presents with sodium 122 mEq/L and normal volume status. What mechanism is most likely at play?
- A Excess water excretion producing hypernatremia
- B Water retention diluting serum sodium
- C Inadequate dietary sodium intake over time
- D Excessive sodium loss through ongoing diarrhea
Correct answer: Water retention diluting serum sodium
SIADH causes inappropriate ADH release → water retention and dilutional hyponatremia despite normal or increased volume.
A patient with serum magnesium 0.9 mg/dL complains of palpitations and muscle weakness. Which electrolyte imbalance should the nurse also assess for?
- A Hypernatremia
- B Hypercalcemia
- C Hypokalemia
- D Hypermagnesemia
Correct answer: Hypokalemia
Hypomagnesemia often accompanies or causes refractory hypokalemia due to renal potassium loss mechanisms.
What finding is characteristic of hyponatremia?
- A Serum sodium 148 mEq/L
- B Confusion and seizures
- C Dry mucous membranes only
- D Hyperreflexia and muscle spasms
Correct answer: Confusion and seizures
Hyponatremia can cause cerebral edema → confusion, seizures; dry mucous membranes may accompany but are less specific; 148 is hypernatremia.
A patient with chronic alcoholism has magnesium 3.0 mg/dL, hypotension, bradycardia and lethargy. What condition is this?
- A Hypomagnesemia
- B Hypermagnesemia
- C Hypocalcemia
- D Hypernatremia
Correct answer: Hypermagnesemia
A magnesium above ~2.1 mg/dL indicates hypermagnesemia; signs include lethargy, hypotension, bradycardia from neuromuscular/cardiac depression.
Which electrolyte imbalance is most likely in a patient with pancreatitis due to fat saponification?
- A Hypercalcemia
- B Hypocalcemia
- C Hypernatremia
- D Hypomagnesemia
Correct answer: Hypocalcemia
Pancreatitis can lead to hypocalcemia via fat saponification (calcium binds fat) thereby dropping serum calcium.
Which clinical feature is most consistent with hypokalemia (3.0 mEq/L)?
- A Hyperactive bowel sounds and diarrhea
- B U-waves on ECG and muscle weakness
- C Peaked T-waves and bradycardia
- D Shortened QT interval and hyperreflexia
Correct answer: U-waves on ECG and muscle weakness
Hypokalemia causes ECG U-waves, muscle weakness, and may cause hypoactive bowel sounds; peaked T-waves are hyperkalemia.
A nurse observes a patient with serum sodium of 160 mEq/L being restless, flushed and dehydrated. What is the most appropriate nursing intervention?
- A Rapidly infuse hypotonic fluid to drop sodium quickly
- B Administer hypertonic saline to raise serum sodium
- C Slowly infuse isotonic/hypotonic fluid with monitoring
- D Administer a loop diuretic immediately to excrete sodium
Correct answer: Slowly infuse isotonic/hypotonic fluid with monitoring
In hypernatremia, the correct approach is to lower sodium slowly to avoid cerebral edema; rapid correction or wrong fluid can cause harm.
A patient with primary hyperparathyroidism presents with fatigue, polyuria, and serum calcium 11.4 mg/dL. Which intervention is likely included in the plan?
- A Encourage a high dietary calcium intake daily
- B Provide hydration followed by a loop diuretic
- C Give intravenous magnesium supplementation
- D Restrict only dietary sodium while observing
Correct answer: Provide hydration followed by a loop diuretic
Hypercalcemia often requires hydration and loop diuretics to enhance calcium excretion; encouraging dietary calcium would worsen the condition.
Which electrolyte imbalance would you suspect in a patient receiving high-dose cisplatin chemotherapy with persistent vomiting and decreased intake?
- A Hypermagnesemia
- B Hypernatremia
- C Hypomagnesemia
- D Hypercalcemia
Correct answer: Hypomagnesemia
Cisplatin and vomiting cause renal magnesium wasting and GI losses → hypomagnesemia.