Fluid & electrolyte imbalances NCLEX-RN Practice Questions

Fluid & electrolyte imbalances NCLEX-RN Practice Questions

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Fluid & Electrolyte Imbalances NCLEX-RN Practice Questions

Mastering fluid and electrolyte imbalances is essential for success on the NCLEX-RN and safe clinical practice. This topic-wise question set is designed to sharpen your clinical judgment in scenarios involving sodium, potassium, calcium, magnesium, phosphate, and fluid volume disturbances. You will encounter real-world nursing priorities, such as assessing neuromuscular status, interpreting ECG changes, selecting appropriate IV fluids, prioritizing interventions, and evaluating responses to therapy. Each question reflects Physiological Adaptation competencies expected of entry-level RNs, with emphasis on safety, critical thinking, and evidence-based care. Use these questions to solidify your understanding, recognize red flags, and confidently apply interventions that stabilize patients with complex fluid and electrolyte disorders.

Q1. A patient with severe vomiting for 48 hours presents with weakness and a flat T wave on ECG. Which intervention is the priority?

  • Administer IV 0.9% sodium chloride with 40 mEq potassium chloride as prescribed
  • Administer IV 3% hypertonic saline
  • Start an insulin and dextrose infusion
  • Give oral sodium bicarbonate tablets

Correct Answer: Administer IV 0.9% sodium chloride with 40 mEq potassium chloride as prescribed

Q2. A patient with heart failure on furosemide reports muscle cramps and palpitations. Which lab result requires immediate action?

  • Potassium 2.9 mEq/L
  • Sodium 133 mEq/L
  • Magnesium 1.7 mg/dL
  • Calcium 8.8 mg/dL

Correct Answer: Potassium 2.9 mEq/L

Q3. A client with SIADH has serum sodium of 121 mEq/L and confusion. Which provider order should the nurse question?

  • 0.45% normal saline at 125 mL/hr
  • Fluid restriction to 800 mL/day
  • Oral salt tablets
  • Seizure precautions

Correct Answer: 0.45% normal saline at 125 mL/hr

Q4. Which assessment finding best indicates improvement in a client treated for hypernatremia due to dehydration?

  • Serum sodium decreases from 156 to 144 mEq/L
  • Urine output decreases to 20 mL/hr
  • Weight decreases by 1.5 kg in 24 hours
  • Serum osmolality increases to 310 mOsm/kg

Correct Answer: Serum sodium decreases from 156 to 144 mEq/L

Q5. A postoperative client on NG suction develops muscle twitching and positive Chvostek’s sign. Which electrolyte imbalance is most likely?

  • Hypocalcemia
  • Hypermagnesemia
  • Hyperkalemia
  • Hyperphosphatemia

Correct Answer: Hypocalcemia

Q6. A client with diabetic ketoacidosis is started on insulin infusion. Which electrolyte should the nurse monitor most closely during the first 4 hours?

  • Potassium
  • Calcium
  • Sodium
  • Chloride

Correct Answer: Potassium

Q7. Which IV fluid is most appropriate for initial resuscitation of a patient with hypovolemic shock from hemorrhage?

  • 0.9% sodium chloride
  • 0.45% sodium chloride
  • D5W
  • 3% sodium chloride

Correct Answer: 0.9% sodium chloride

Q8. A client with end-stage renal disease presents with peaked T waves and weakness. Which intervention is priority?

  • Administer IV calcium gluconate
  • Administer oral polystyrene sulfonate
  • Encourage high-potassium foods
  • Start 0.45% saline infusion

Correct Answer: Administer IV calcium gluconate

Q9. The nurse reviews labs: Na 128 mEq/L, serum osmolality 265 mOsm/kg, urine specific gravity 1.030. What is the likely diagnosis?

  • SIADH
  • Diabetes insipidus
  • Hyperglycemic hyperosmolar state
  • Metabolic alkalosis

Correct Answer: SIADH

Q10. A patient with acute pancreatitis develops numbness around the mouth and carpopedal spasm. Which additional finding supports the suspected imbalance?

  • Prolonged QT interval
  • Shortened QT interval
  • Widened QRS complex
  • Peaked T waves

Correct Answer: Prolonged QT interval

Q11. A client with chronic alcoholism is at risk for hypomagnesemia. Which assessment is most consistent with this imbalance?

  • Hyperactive deep tendon reflexes and PVCs
  • Flaccid muscles and hypotension
  • Bradycardia and diminished reflexes
  • Facial flushing and prolonged PR interval

Correct Answer: Hyperactive deep tendon reflexes and PVCs

Q12. Which order is appropriate for severe symptomatic hyponatremia (Na 118 mEq/L) with seizures?

  • 3% sodium chloride via central line with frequent sodium monitoring
  • D5W at 125 mL/hr
  • 0.45% sodium chloride at 75 mL/hr
  • Free water via enteral tube feeding

Correct Answer: 3% sodium chloride via central line with frequent sodium monitoring

Q13. A 24-hour postoperative patient on NG suction shows ABG: pH 7.50, PaCO2 42 mm Hg, HCO3- 33 mEq/L. Which electrolyte change is most expected?

  • Hypokalemia
  • Hyperkalemia
  • Hypermagnesemia
  • Hyperphosphatemia

Correct Answer: Hypokalemia

Q14. Which assessment best indicates fluid volume overload in a patient with heart failure receiving IV fluids?

  • New bibasilar crackles and S3 heart sound
  • Dry mucous membranes and orthostatic hypotension
  • Tenting skin turgor and flat neck veins
  • Urine specific gravity 1.005

Correct Answer: New bibasilar crackles and S3 heart sound

Q15. The nurse receives a lab: Calcium 6.9 mg/dL, Phosphate 5.5 mg/dL. Which condition could explain this?

  • Chronic kidney disease
  • Primary hyperparathyroidism
  • Prolonged immobilization
  • Vitamin D intoxication

Correct Answer: Chronic kidney disease

Q16. Which client is most at risk for hypernatremia?

  • An elderly patient with fever, delirium, and limited access to water
  • A client with Addison disease and vomiting
  • A postoperative client receiving hypotonic fluids
  • A patient with SIADH on fluid restriction

Correct Answer: An elderly patient with fever, delirium, and limited access to water

Q17. A burn patient (30% TBSA) is in the first 8 hours post-injury. Which finding indicates effective fluid resuscitation?

  • Urine output 0.5–1 mL/kg/hr
  • Serum sodium increases to 155 mEq/L
  • Lactate rises from 2.0 to 4.5 mmol/L
  • Mean arterial pressure drops to 55 mm Hg

Correct Answer: Urine output 0.5–1 mL/kg/hr

Q18. A patient taking spironolactone needs dietary teaching. Which statement indicates understanding?

  • I will avoid salt substitutes that contain potassium
  • I will increase bananas and orange juice in my diet
  • I will take an over-the-counter potassium supplement daily
  • I will restrict foods high in sodium and increase licorice intake

Correct Answer: I will avoid salt substitutes that contain potassium

Q19. A client with diabetes insipidus presents with intense thirst, polyuria, and Na 154 mEq/L. Which intervention is anticipated?

  • Desmopressin administration and hypotonic fluids
  • Loop diuretic therapy and hypertonic saline
  • Fluid restriction and demeclocycline
  • Insulin infusion with dextrose

Correct Answer: Desmopressin administration and hypotonic fluids

Q20. A client receiving total parenteral nutrition develops weakness and arrhythmias after restarting feeds. Which electrolyte imbalance is most likely?

  • Hypophosphatemia
  • Hypermagnesemia
  • Hypercalcemia
  • Hyponatremia

Correct Answer: Hypophosphatemia

Q21. Which finding is a hallmark of hyperkalemia on ECG?

  • Tall peaked T waves
  • Presence of U waves
  • QT prolongation
  • ST-segment elevation with reciprocal changes

Correct Answer: Tall peaked T waves

Q22. A patient with cirrhosis and ascites is receiving spironolactone and fluid restriction. Which lab requires follow-up?

  • Potassium 5.6 mEq/L
  • Sodium 132 mEq/L
  • Albumin 2.8 g/dL
  • Ammonia 55 µmol/L

Correct Answer: Potassium 5.6 mEq/L

Q23. A client with serum calcium 12.2 mg/dL is on IV normal saline. Which additional order assists in lowering calcium?

  • Administer IV loop diuretic after rehydration
  • Start thiazide diuretic therapy
  • Restrict mobility to bedrest
  • Begin high-calcium diet

Correct Answer: Administer IV loop diuretic after rehydration

Q24. Which assessment is priority for a patient receiving IV magnesium sulfate for preeclampsia?

  • Deep tendon reflexes and respiratory rate
  • Pupillary reaction and capillary refill
  • Oral mucosa and skin turgor
  • Bowel sounds and abdominal girth

Correct Answer: Deep tendon reflexes and respiratory rate

Q25. A patient on digoxin has nausea and visual halos. Potassium is 2.8 mEq/L. What is the nurse’s priority action?

  • Notify provider and hold digoxin
  • Administer sodium polystyrene sulfonate
  • Increase loop diuretic dose
  • Encourage intake of distilled water

Correct Answer: Notify provider and hold digoxin

Q26. A patient with tumor lysis syndrome has potassium 6.2 mEq/L and phosphate 6.0 mg/dL. Which prescription requires clarification?

  • Potassium phosphate IV supplementation
  • Continuous cardiac monitoring
  • Insulin with dextrose infusion
  • IV normal saline hydration

Correct Answer: Potassium phosphate IV supplementation

Q27. Which nursing intervention prevents hyponatremia in a marathon runner admitted with heat exhaustion?

  • Encourage oral rehydration solution with balanced electrolytes
  • Provide free water ad lib
  • Restrict oral intake to less than 500 mL/day
  • Administer 3% saline bolus

Correct Answer: Encourage oral rehydration solution with balanced electrolytes

Q28. A client with COPD exacerbation is receiving high-dose loop diuretics for cor pulmonale. Which lab should be monitored to reduce risk of dysrhythmias?

  • Potassium and magnesium
  • Calcium and phosphate
  • Sodium and chloride
  • Albumin and total protein

Correct Answer: Potassium and magnesium

Q29. A patient with severe hyponatremia is started on hypertonic saline. Which action is essential to prevent osmotic demyelination syndrome?

  • Limit sodium correction to no more than 8–10 mEq/L in 24 hours
  • Maintain serum sodium above 150 mEq/L within 6 hours
  • Switch to D5W once sodium reaches 125 mEq/L
  • Administer loop diuretic boluses every hour

Correct Answer: Limit sodium correction to no more than 8–10 mEq/L in 24 hours

Q30. A patient on long-term proton pump inhibitor therapy presents with tetany. Which lab abnormality is most consistent?

  • Hypomagnesemia
  • Hypernatremia
  • Hyperkalemia
  • Hyperphosphatemia

Correct Answer: Hypomagnesemia

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