Lab Value Interpretation NCLEX-RN Practice Questions help you translate numbers into safe, priority-based nursing actions. In the Reduction of Risk Potential domain, nurses must recognize critical lab trends, anticipate complications, and intervene early to prevent harm. This topic-wise question set focuses on interpreting ABGs, CBC, chemistries, coagulation profiles, cardiac markers, endocrine values, therapeutic drug levels, and special tests (e.g., lactate, ammonia, osmolality). Each item is designed to mirror real clinical decisions—what to do first, whom to notify, what to hold, and which therapy to anticipate—so you can confidently prioritize care. Work through the scenarios, note normal ranges, and practice turning lab data into appropriate actions that reduce risk and promote patient safety.
Q1. A hemodialysis patient reports weakness. Labs: K+ 6.2 mEq/L, creatinine 7.0 mg/dL, peaked T waves on ECG. Which immediate nursing action reduces the greatest risk?
- Administer furosemide 40 mg IV now
- Place the patient on continuous cardiac monitoring
- Start IV potassium chloride replacement
- Encourage intake of potassium-rich foods
Correct Answer: Place the patient on continuous cardiac monitoring
Q2. A client on warfarin for atrial fibrillation has an INR of 5.4 and reports new-onset epistaxis. What is the nurse’s priority action?
- Administer the scheduled warfarin dose and reassess INR in the morning
- Hold warfarin and notify the provider of the supratherapeutic INR
- Encourage increased green leafy vegetables to lower INR
- Administer aspirin 81 mg for clot prevention
Correct Answer: Hold warfarin and notify the provider of the supratherapeutic INR
Q3. A patient on an unfractionated heparin infusion has an aPTT of 120 seconds (control 30 seconds). Which action is most appropriate?
- Stop the heparin infusion and notify the provider
- Increase the heparin infusion by 2 units/kg/hr
- Administer warfarin now to lower aPTT
- No action is needed; this is therapeutic
Correct Answer: Stop the heparin infusion and notify the provider
Q4. Which arterial blood gas (ABG) set most strongly supports diabetic ketoacidosis (DKA)?
- pH 7.52, PaCO2 28 mmHg, HCO3− 24 mEq/L
- pH 7.28, PaCO2 25 mmHg, HCO3− 12 mEq/L
- pH 7.45, PaCO2 40 mmHg, HCO3− 24 mEq/L
- pH 7.50, PaCO2 45 mmHg, HCO3− 32 mEq/L
Correct Answer: pH 7.28, PaCO2 25 mmHg, HCO3− 12 mEq/L
Q5. After a head injury, a patient has Na+ 124 mEq/L, serum osmolality 260 mOsm/kg, urine specific gravity 1.030, and urine osmolality 600 mOsm/kg. Which intervention is priority?
- Increase free water intake
- Administer IV hypotonic saline
- Implement fluid restriction and monitor neurologic status
- Administer desmopressin
Correct Answer: Implement fluid restriction and monitor neurologic status
Q6. A patient on lithium for bipolar disorder has a trough level of 2.1 mEq/L and reports nausea and coarse tremors. What should the nurse do first?
- Administer the next lithium dose with food
- Hold lithium and notify the provider immediately
- Encourage increased fluid and salt restriction
- Start a diuretic to enhance lithium excretion
Correct Answer: Hold lithium and notify the provider immediately
Q7. A client on digoxin has a level of 2.8 ng/mL, HR 46/min, and new visual halos. Which medication should the nurse anticipate administering?
- Atropine IV
- Digoxin-specific antibody fragments (digoxin immune Fab)
- Calcium gluconate IV
- Lidocaine IV
Correct Answer: Digoxin-specific antibody fragments (digoxin immune Fab)
Q8. A patient with acute pancreatitis has lipase 820 U/L and severe epigastric pain. Which immediate order is most appropriate?
- Advance to clear liquids
- Keep NPO and administer IV fluids
- Start high-fat diet for caloric support
- Administer acetaminophen only, avoid opioids
Correct Answer: Keep NPO and administer IV fluids
Q9. A client with suspected thyroid storm shows TSH 0.01 µIU/mL, markedly elevated T3/T4, HR 150, and hyperthermia. Which medication is the immediate priority?
- Levothyroxine
- Propranolol
- Prednisone
- Desmopressin
Correct Answer: Propranolol
Q10. A client with chronic kidney disease has Ca2+ 7.2 mg/dL and phosphate 6.4 mg/dL. Which nursing action best reduces immediate risk?
- Encourage weight-bearing exercise
- Place the client on seizure precautions
- Administer potassium supplements
- Increase dairy intake
Correct Answer: Place the client on seizure precautions
Q11. A patient with suspected sepsis has a lactate of 5.8 mmol/L, BP 86/50, HR 124. Which action is priority?
- Administer vasodilators
- Initiate large-bore IV access and give isotonic crystalloid bolus per protocol
- Restrict fluids until cultures result
- Administer oral antibiotics
Correct Answer: Initiate large-bore IV access and give isotonic crystalloid bolus per protocol
Q12. A trauma patient has CK 18,000 U/L, dark urine, K+ 5.8 mEq/L, and rising creatinine. What is the priority intervention?
- Administer loop diuretics only
- Aggressive IV isotonic fluids to maintain high urine output
- Restrict fluids to prevent edema
- Start protein supplements
Correct Answer: Aggressive IV isotonic fluids to maintain high urine output
Q13. Postoperative patient is anxious with ABG: pH 7.52, PaCO2 28 mmHg, HCO3− 24 mEq/L. Which intervention is most appropriate?
- Increase oxygen to 10 L/min by NRB
- Coach slow, diaphragmatic breathing and treat pain
- Administer sodium bicarbonate
- Intubate immediately
Correct Answer: Coach slow, diaphragmatic breathing and treat pain
Q14. A postpartum client with bleeding shows platelets 60,000/µL, fibrinogen 90 mg/dL, prolonged PT/aPTT, and elevated D-dimer. Which therapy should the nurse anticipate?
- Vitamin K only
- Heparin infusion
- Cryoprecipitate and platelets
- Warfarin loading dose
Correct Answer: Cryoprecipitate and platelets
Q15. A patient with dyspnea has BNP 1,800 pg/mL and bibasilar crackles. Which action is most appropriate?
- Encourage 2 liters of oral fluids
- Place in high Fowler’s and administer IV loop diuretic as prescribed
- Start high-sodium diet
- Discontinue cardiac monitoring
Correct Answer: Place in high Fowler’s and administer IV loop diuretic as prescribed
Q16. A client presents with chest pressure now resolved. Troponin I was 0.02 ng/mL, now 0.78 ng/mL at 3 hours. What is the priority action?
- Schedule an outpatient stress test next week
- Notify the provider immediately and maintain NPO for possible emergent PCI
- Ambulate to the bathroom to reduce anxiety
- Give high-dose ibuprofen
Correct Answer: Notify the provider immediately and maintain NPO for possible emergent PCI
Q17. A client scheduled for CT with IV contrast has creatinine 2.4 mg/dL and takes metformin. Which action best reduces risk?
- Administer metformin with sips of water before the scan
- Hold metformin and notify the provider due to renal dysfunction
- Encourage high-protein supplements pre-scan
- No changes; proceed as planned
Correct Answer: Hold metformin and notify the provider due to renal dysfunction
Q18. A malnourished alcoholic patient has magnesium 1.1 mg/dL and prolonged QT on ECG. Which action is priority?
- Administer oral magnesium oxide only
- Initiate seizure precautions and prepare to administer IV magnesium sulfate
- Restrict fluids to prevent edema
- Administer calcium channel blockers
Correct Answer: Initiate seizure precautions and prepare to administer IV magnesium sulfate
Q19. A cirrhotic patient is increasingly confused. Labs: ammonia 96 µg/dL, INR 2.4 (not on warfarin), albumin 2.1 g/dL, AST/ALT elevated. Which medication should the nurse anticipate?
- Lactulose
- Warfarin
- Acetaminophen
- Metformin
Correct Answer: Lactulose
Q20. A COPD patient on 6 L/min nasal cannula becomes somnolent. ABG: pH 7.32, PaCO2 60 mmHg, HCO3− 32 mEq/L. Which action is most appropriate?
- Titrate oxygen to maintain SpO2 88–92% and notify the provider
- Increase oxygen to 15 L by NRB mask
- Administer sodium bicarbonate
- Discontinue oxygen therapy
Correct Answer: Titrate oxygen to maintain SpO2 88–92% and notify the provider
Q21. A 32-week pregnant client with severe preeclampsia has platelets 85,000/µL and AST/ALT 3× normal. Which action is priority?
- Proceed with epidural anesthesia as planned
- Notify the provider and prepare to administer magnesium sulfate
- Encourage high-sodium diet
- Administer aspirin 325 mg
Correct Answer: Notify the provider and prepare to administer magnesium sulfate
Q22. A patient receiving chemotherapy has K+ 6.5 mEq/L, uric acid 10 mg/dL, phosphate 6.8 mg/dL, calcium 6.8 mg/dL. Which immediate intervention reduces life-threatening risk?
- Administer allopurinol only
- Initiate continuous cardiac monitoring and prepare to give IV calcium gluconate
- Start oral phosphate supplements
- Encourage potassium-rich foods
Correct Answer: Initiate continuous cardiac monitoring and prepare to give IV calcium gluconate
Q23. An older adult with type 2 diabetes presents with glucose 880 mg/dL, serum osmolality 330 mOsm/kg, pH 7.38, minimal ketones. What is the priority therapy?
- IV insulin bolus only
- Aggressive IV isotonic fluid resuscitation
- Immediate bicarbonate infusion
- High-dose subcutaneous insulin only
Correct Answer: Aggressive IV isotonic fluid resuscitation
Q24. A patient on epoetin alfa for CKD has hemoglobin 13.4 g/dL and hematocrit 41%. What should the nurse do?
- Administer epoetin as scheduled
- Hold epoetin and notify the provider due to elevated hemoglobin
- Increase epoetin dose to reach Hgb 15 g/dL
- Administer IV iron sucrose immediately
Correct Answer: Hold epoetin and notify the provider due to elevated hemoglobin
Q25. A patient receiving vancomycin has a trough of 24 mcg/mL and new rise in creatinine. What is the best nursing action?
- Administer the next dose now
- Hold the dose and notify the provider for dose adjustment
- Double the infusion rate to shorten exposure
- Switch to oral vancomycin without notifying the provider
Correct Answer: Hold the dose and notify the provider for dose adjustment
Q26. A patient on phenytoin has total level 7 mcg/mL and albumin 2.0 g/dL with no seizures. What is the most appropriate action?
- Increase phenytoin dose immediately
- Request a free (unbound) phenytoin level before adjusting the dose
- Stop phenytoin due to low albumin
- Start valproate concurrently
Correct Answer: Request a free (unbound) phenytoin level before adjusting the dose
Q27. Labs: Na+ 138 mEq/L, Cl− 100 mEq/L, HCO3− 14 mEq/L. Which condition is most consistent with this anion gap pattern?
- Vomiting-induced metabolic alkalosis
- Diarrhea with normal anion gap acidosis
- Lactic acidosis from septic shock
- Hyperaldosteronism
Correct Answer: Lactic acidosis from septic shock
Q28. Which cerebrospinal fluid (CSF) profile best indicates bacterial meningitis?
- Low opening pressure, low neutrophils, high glucose
- High opening pressure, high neutrophils, low glucose, high protein
- Normal opening pressure, lymphocyte predominance, normal glucose
- High glucose, low protein, eosinophil predominance
Correct Answer: High opening pressure, high neutrophils, low glucose, high protein
Q29. Urinalysis shows positive nitrites and leukocyte esterase, WBCs >10/hpf, and many squamous epithelial cells. What action best reduces the risk of a false result?
- Start antibiotics immediately without repeat testing
- Obtain a repeat clean-catch midstream specimen after teaching proper technique
- Add vitamin C to the sample
- Refrigerate the same sample for 24 hours before retesting
Correct Answer: Obtain a repeat clean-catch midstream specimen after teaching proper technique
Q30. Six hours after total thyroidectomy, the patient has perioral tingling and an ionized calcium of 0.98 mmol/L (low). Which action is priority?
- Encourage deep breathing and coughing
- Prepare to administer IV calcium gluconate
- Increase dietary calcium when tolerated
- Administer loop diuretics
Correct Answer: Prepare to administer IV calcium gluconate
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