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Fluids and Electrolytes NCLEX practice questions
Electrolyte imbalances show up in almost every med-surg topic. These questions cover the signs of high and low potassium, sodium, calcium and magnesium, IV solutions and fluid balance, and the priority action for each.
Question 1 · Physiological Adaptation
A client with severe dehydration and hypotension develops decreased urine output and rising creatinine. The nurse recognizes this presentation is most consistent with which type of acute kidney injury?
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Answer: C. Prerenal acute kidney injury results from decreased perfusion to the kidneys, such as from dehydration and hypotension, and is often reversible with fluid resuscitation. Postrenal AKI is caused by obstruction of urine outflow rather than a perfusion problem. Intrarenal AKI involves direct damage to kidney tissue, such as from nephrotoxins or prolonged ischemia. Chronic kidney disease develops gradually over months to years, not acutely from a single episode of dehydration.
Checked against: OpenStax Medical-Surgical Nursing, 35.6
Question 2 · Pharmacological and Parenteral Therapies
A client is scheduled for hemodialysis. Which medication should the nurse plan to hold before treatment?
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Answer: C. Antihypertensives are typically held before hemodialysis because dialysis itself lowers blood pressure, and combining the two can cause severe hypotension. Insulin needs are managed based on current blood glucose rather than being routinely held. Antibiotic timing may be adjusted around dialysis sessions but is not automatically withheld. Anticoagulants require individualized provider evaluation and are not a standard pre-dialysis hold in this scenario.
Checked against: pubmed.ncbi.nlm.nih.gov; pmc.ncbi.nlm.nih.gov
Question 3 · Pharmacological and Parenteral Therapies
A nurse is explaining why 3% saline is typically administered through a central venous catheter rather than a peripheral IV. Which explanation is most accurate?
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Answer: C. Hypertonic solutions like 3% saline have a high osmolarity that can irritate and damage smaller peripheral veins, causing phlebitis, so a central line with greater blood flow to dilute the solution is preferred. Central lines are not chosen simply to allow faster rates; hypertonic saline must still be given slowly regardless of the type of line, due to the risk of rapid fluid shifts. Peripheral IVs are used for many other types of fluids, just not preferred for hypertonic solutions like this one.
Checked against: OpenStax Pharmacology for Nurses, 5.3; OpenStax Clinical Nursing Skills, 13.2
Question 4 · Safety and Infection Control
Fifteen minutes after starting a blood transfusion, a client develops fever, chills, and lower back pain. What is the nurse's first action?
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Answer: C. The first action when a transfusion reaction is suspected is to stop the blood immediately, disconnect the blood tubing, and keep the line open with new saline and new tubing while staying with the client and then notifying the provider. Slowing the rate still exposes the client to more of the possibly incompatible blood. Giving acetaminophen and continuing the transfusion delays necessary intervention and could worsen a serious reaction. Waiting for provider orders before stopping the transfusion is unsafe, since stopping the infusion is an immediate independent nursing action.
Checked against: OpenStax Clinical Nursing Skills, 13.4
Question 5 · Physiological Adaptation
A client has a serum calcium level of 7.8 mg/dL. Which findings should the nurse anticipate? Select all that apply.
Select all that apply.
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Answer: A, B, C, E. Hypocalcemia produces neuromuscular irritability, evidenced by positive Trousseau and Chvostek signs, tingling, tetany, and a prolonged QT interval on ECG. Bone pain, kidney stones, and constipation with confusion are manifestations of hypercalcemia, the opposite imbalance, so they should not be selected here.
Checked against: OpenStax Medical-Surgical Nursing, 10.3; OpenStax Clinical Nursing Skills, 19.1
Question 6 · Reduction of Risk Potential
The nurse notes U waves on a client's ECG tracing. Which laboratory result would the nurse anticipate?
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Answer: B. U waves on the ECG are a hallmark finding of hypokalemia, along with flattened T waves; patients on diuretics are at particular risk and should be monitored closely. High potassium instead produces peaked T waves and a widened QRS, the opposite ECG pattern. Low calcium classically prolongs the QT interval rather than producing U waves, and high magnesium is more associated with bradycardia and hyporeflexia than U waves.
Checked against: OpenStax Fundamentals of Nursing, 20.1
Question 7 · Physiological Adaptation
A client reports intense thirst and is found to have dry, sticky mucous membranes and increasing restlessness. Which electrolyte imbalance does the nurse suspect?
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Answer: D. Intense thirst, dry sticky mucous membranes, and restlessness that can progress to seizures are classic manifestations of hypernatremia caused by a relative excess of sodium compared to water. Hyponatremia instead presents with confusion and lethargy due to low sodium, not thirst. Hypokalemia causes muscle weakness and U waves, and hypocalcemia causes tetany and Trousseau/Chvostek signs, none of which match this presentation.
Checked against: OpenStax Pharmacology for Nurses, 5.2; OpenStax Fundamentals of Nursing, 20.3
Question 8 · Reduction of Risk Potential
Which electrolyte imbalance produces clinical manifestations that mirror hypocalcemia, such as tetany and a positive Trousseau sign?
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Answer: B. Hyperphosphatemia often drives serum calcium down through a reciprocal relationship, producing symptoms that mirror hypocalcemia, including tetany, muscle cramps, and a positive Trousseau/Chvostek sign. Hypophosphatemia instead causes muscle weakness and risk for respiratory failure, an entirely different picture. Hyperkalemia causes peaked T waves and muscle twitching, and hypernatremia causes thirst and dry mucous membranes, neither of which resembles hypocalcemia.
Checked against: openstax.org
Question 9 · Reduction of Risk Potential
A client receiving IV fluids for dehydration develops new-onset dyspnea, crackles in bilateral lung bases, and a 3-lb weight gain over 24 hours. Which action should the nurse take first?
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Answer: C. These findings indicate fluid volume overload; the priority action is to slow or stop the infusion and notify the provider so treatment such as a diuretic can be initiated. Increasing the fluid rate would worsen the overload and respiratory distress. Lying flat would worsen dyspnea in fluid overload, since the client should instead be positioned upright. An antihistamine does not treat fluid overload and is not indicated for this presentation.
Checked against: OpenStax Medical-Surgical Nursing, 10.2; OpenStax Clinical Nursing Skills, 13.3
Question 10 · Management of Care
A nurse notes that a postoperative client's urine output has been 20 mL/hr for the past two hours. What is the nurse's priority action?
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Answer: B. The minimum acceptable urine output for an adult is 30 mL/hr; output below this suggests renal hypoperfusion and must be reported promptly rather than simply documented. Increasing the IV rate independently is outside the nurse's scope without a provider order. Waiting four hours to recheck delays necessary intervention for a potentially serious problem affecting kidney perfusion.
Checked against: OpenStax Maternal-Newborn Nursing, 21.2
Question 11 · Physiological Adaptation
The nurse is caring for a client one day after a thyroidectomy. Which electrolyte imbalance is the priority concern?
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Answer: A. During thyroidectomy, the parathyroid glands may be inadvertently injured or removed, leading to hypocalcemia; the nurse should monitor for tingling, tetany, and a positive Trousseau or Chvostek sign. Hypercalcemia would be unexpected in this situation since parathyroid function (which raises calcium) is typically impaired, not enhanced. Hyperkalemia and hyponatremia are not directly related to parathyroid injury following thyroid surgery.
Checked against: OpenStax Medical-Surgical Nursing, 10.3
Question 12 · Reduction of Risk Potential
A client is admitted with a serum sodium level of 128 mEq/L. Which symptom would the nurse expect to find?
Show answer and rationale
Answer: C. Hyponatremia is characterized by confusion, lethargy, headache, nausea, and seizures if severe due to cerebral cell swelling from low extracellular sodium. Intense thirst and dry mucous membranes describe hypernatremia, the opposite imbalance. Tetany and tingling are signs of hypocalcemia, and bone pain with kidney stones is associated with hypercalcemia, not a sodium disturbance.
Checked against: OpenStax Pharmacology for Nurses, 5.2
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Frequently asked questions
What electrolytes are most tested on the NCLEX?
Potassium, sodium, calcium and magnesium come up constantly, along with fluid volume excess and deficit and choosing the right IV fluid. The cheat sheets linked below summarize the signs of each imbalance.
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About these questions
Every question on this page was approved by a licensed RN, and its answer was checked against open nursing references (mostly OpenStax nursing textbooks) before publishing. They are NCLEX-style practice, not real NCLEX items. NurseLingo is not affiliated with NCSBN. Spot a problem? Tell us.