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NCLEX-RN Laboratory values practice questions

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These are original practice items written to the NCLEX-RN blueprint (4 options, no penalty for wrong answers), not actual exam questions. Try each one before you open the answer.

What this topic covers

Laboratory values sits inside the Reduction of Risk Potential category of the NCLEX-RN. Our bank holds 38 verified items tagged to it, and the 4 below are a fixed sample so the page stays the same every time you open it. Each one shows the reasoning, not just the letter.

The topic tag comes from our own items rather than from a published syllabus, so treat it as a map of what we cover. For the official category breakdown see the NCLEX-RN page.

Laboratory values sample questions

Question 1

A 55-year-old client with chronic kidney disease stage 3 is admitted for elective hernia repair. Preoperative laboratory results show serum potassium 5.8 mEq/L, serum creatinine 2.4 mg/dL, blood urea nitrogen 42 mg/dL, and hemoglobin 10.2 g/dL. Which laboratory value is most concerning for the perioperative period?

  1. A Blood urea nitrogen 42 mg/dL
  2. B Serum creatinine 2.4 mg/dL
  3. C Serum potassium 5.8 mEq/L
  4. D Hemoglobin 10.2 g/dL
Show the answer and explanation

Correct answer: C

A potassium of 5.8 mEq/L is elevated, and anesthesia, surgical tissue injury, and some anesthetic drugs can raise it further, increasing the risk of dangerous dysrhythmias. It is the value most likely to affect perioperative safety and must be reported and corrected before surgery.

Why the other options are wrong:
A: A BUN of 42 mg/dL is elevated but expected with stage 3 chronic kidney disease.
B: A creatinine of 2.4 mg/dL reflects the client's known chronic kidney disease and is not an acute threat.
D: A hemoglobin of 10.2 g/dL reflects mild anemia, which is common in chronic kidney disease.

Question 2

A 66-year-old client with chronic kidney disease stage 4 is admitted for evaluation of fatigue and muscle cramps. The nurse reviews the morning laboratory results: serum potassium 6.2 mEq/L, serum creatinine 3.8 mg/dL, and BUN 68 mg/dL. Which assessment finding requires the most immediate nursing action?

  1. A The urine output over the last 8 hours is 380 mL.
  2. B The client's blood pressure is 148/92 mm Hg and pedal edema is 1+.
  3. C The cardiac monitor shows peaked T waves with a heart rate of 62.
  4. D The client reports mild nausea and loss of appetite.
Show the answer and explanation

Correct answer: C

Peaked T waves show that hyperkalemia is already affecting cardiac conduction, which can progress to ventricular fibrillation or asystole. This client needs immediate treatment, beginning with measures to stabilize the heart and lower potassium.

Why the other options are wrong:
A: 380 mL over 8 hours is about 47 mL/hr, which is adequate output.
B: Mild hypertension and 1+ edema are expected in chronic kidney disease and are not immediately life-threatening.
D: Nausea and poor appetite are common with uremia and are not immediately dangerous.

Question 3

A 72-year-old client is admitted to the medical unit for dehydration. The nurse reviews the laboratory results: serum sodium 151 mEq/L, serum potassium 4.1 mEq/L, blood glucose 148 mg/dL, and serum creatinine 1.2 mg/dL. Which result should the nurse report to the provider first?

  1. A Serum potassium 4.1 mEq/L
  2. B Serum creatinine 1.2 mg/dL
  3. C Blood glucose 148 mg/dL
  4. D Serum sodium 151 mEq/L
Show the answer and explanation

Correct answer: D

A sodium of 151 mEq/L is above the normal range of 135 to 145 mEq/L. Hypernatremia from dehydration pulls water out of brain cells and can cause confusion and seizures, especially in an older adult, so it should be reported first.

Why the other options are wrong:
A: A potassium of 4.1 mEq/L is within the normal range of 3.5 to 5.0 mEq/L.
B: A creatinine of 1.2 mg/dL is at the upper limit of normal and should be followed, but it is not the most urgent value.
C: A glucose of 148 mg/dL is mildly elevated, possibly from stress, and is not an urgent finding.

Question 4

A 68-year-old client in the intensive care unit has the following arterial blood gas results: pH 7.31, PaCO2 50 mm Hg, HCO3- 24 mEq/L. Which condition do these values indicate?

  1. A Metabolic alkalosis with no respiratory compensation
  2. B Respiratory alkalosis with full metabolic compensation
  3. C Respiratory acidosis with no metabolic compensation
  4. D Metabolic acidosis with partial respiratory compensation
Show the answer and explanation

Correct answer: C

The pH of 7.31 shows acidosis, and the PaCO2 of 50 mm Hg is elevated, identifying a respiratory cause. The bicarbonate of 24 mEq/L is normal, so the kidneys have not yet compensated.

Why the other options are wrong:
A: Metabolic alkalosis would show a high pH and a high bicarbonate.
B: Respiratory alkalosis would show a high pH with a low PaCO2.
D: Metabolic acidosis would show a low bicarbonate, which is not present.

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