NCLEX lab values practice questions

Learn the labs that change nursing actions: potassium, sodium, glucose, INR and aPTT, platelets, hemoglobin and creatinine.

1. Question 1

   A client on an inpatient mental health unit takes lithium for bipolar disorder. The client has vomiting, diarrhea and a coarse hand tremor. The lithium level is 1.9 mEq/L (therapeutic 0.6–1.2 mEq/L). Which action should the nurse take?

   • A.Hold the next lithium dose and notify the provider
   • B.Give the lithium dose with a large glass of water
   • C.Teach the client to reduce salt in the diet
   • D.Give an antidiarrheal and continue the usual dose
   Show answer and explanation

   Answer: A

   Lithium has a narrow therapeutic range. A level of 1.9 mEq/L with vomiting, diarrhea and a coarse tremor shows lithium toxicity. The nurse holds the drug, notifies the provider and monitors fluid and sodium balance. Severe toxicity can cause seizures and may need dialysis.

   • A. Correct. The level is above the therapeutic range and the client has signs of toxicity. More lithium would make it worse.
   • B. Fluids help, but giving another dose to a client with toxicity is unsafe.
   • C. Low sodium makes the kidneys keep more lithium, which raises the level further.
   • D. Treating the diarrhea alone ignores the toxic lithium level, which is causing the symptoms.

   Key concept: Lithium levels above 1.5 mEq/L cause toxicity. Dehydration and low sodium raise lithium levels.

   Tip: Lithium and salt are linked: low salt or low water makes lithium climb.

2. Question 2

   A client with a recent head injury has a serum sodium of 120 mEq/L (reference 135–145 mEq/L) and is becoming confused. The provider suspects syndrome of inappropriate antidiuretic hormone (SIADH). Which action should the nurse take?

   • A.Encourage the client to drink at least 3 L of fluid daily
   • B.Hang 0.45% sodium chloride IV
   • C.Start seizure precautions
   • D.Offer a low-sodium diet
   Show answer and explanation

   Answer: C

   In SIADH, the body holds water and dilutes the blood sodium. Low sodium lets water move into brain cells, causing confusion and seizures. The nurse uses seizure precautions, restricts fluids as prescribed, monitors neuro status and follows sodium levels. Sodium must be corrected slowly to avoid nerve damage.

   • A. Extra water dilutes sodium further. Fluid restriction is the usual treatment for SIADH.
   • B. A hypotonic fluid adds free water and would lower the sodium level further.
   • C. Correct. A sodium of 120 mEq/L with new confusion puts the client at risk for seizures from brain swelling.
   • D. Restricting sodium would worsen hyponatremia.

   Key concept: Sodium below about 125 mEq/L, or a fast drop, causes neuro symptoms. Protect the client from seizures.

   Tip: Low sodium, swollen brain: pad the rails and limit water.

3. Question 3

   A client with chronic kidney disease has a serum potassium of 6.4 mEq/L (reference 3.5–5.0 mEq/L). The ECG shows tall, peaked T waves. Which prescription should the nurse question?

   • A.Calcium gluconate 1 g IV over 10 minutes
   • B.Regular insulin 10 units IV with dextrose 50% 25 g
   • C.Potassium chloride 20 mEq by mouth twice daily
   • D.Sodium zirconium cyclosilicate 10 g by mouth
   Show answer and explanation

   Answer: C

   A potassium of 6.4 mEq/L with peaked T waves is a cardiac emergency. Calcium protects the heart, insulin with dextrose shifts potassium into cells, and binders remove it from the body. A potassium supplement would raise the level further, so it is the order the nurse must question.

   • A. IV calcium stabilizes the cardiac cell membrane and protects the heart from dysrhythmias. It is an expected treatment for hyperkalemia with ECG changes.
   • B. Insulin moves potassium into the cells and lowers the serum level within minutes. Dextrose prevents hypoglycemia. This is an expected treatment.
   • C. Correct. Giving more potassium to a client who already has a dangerous potassium level can cause a fatal dysrhythmia. The nurse must hold this order and contact the provider.
   • D. This potassium binder removes potassium through the gut. It is an appropriate treatment for hyperkalemia.

   Key concept: In hyperkalemia, any source of added potassium (supplements, potassium-sparing diuretics, salt substitutes) must be stopped and questioned.

   Tip: Hyperkalemia treatment order: Protect (calcium), Shift (insulin plus dextrose), Remove (binders, diuretics, dialysis).

4. Question 4

   A client with breast cancer that has spread to the bones has a serum calcium of 12.8 mg/dL (reference 8.6–10.2 mg/dL). The client reports constipation and feels weak and tired. Which action should the nurse include in the plan of care?

   • A.Encourage foods high in calcium
   • B.Keep the client on strict bed rest
   • C.Encourage oral fluids as tolerated and as set in the care plan
   • D.Give calcium carbonate with meals
   Show answer and explanation

   Answer: C

   Bone metastases release calcium into the blood. High calcium causes fatigue, weakness, constipation, nausea, confusion, kidney stones and dysrhythmias. Care includes generous fluids (often IV saline), mobility as tolerated, avoiding extra calcium and giving prescribed drugs such as bisphosphonates.

   • A. Adding dietary calcium would raise a level that is already too high.
   • B. Immobility increases calcium release from bones. Movement as tolerated is encouraged.
   • C. Correct. Hydration helps the kidneys excrete calcium and helps prevent kidney stones.
   • D. Calcium supplements are contraindicated when serum calcium is already high.

   Key concept: Hypercalcemia: hydrate, mobilize, avoid calcium; watch the heart and kidneys.

   Tip: High calcium: 'stones, bones, groans and psychiatric overtones.'

5. Question 5

   A client arrives in the emergency department 1 hour after chest pain began. The first troponin result is within normal limits. The client asks, "Does this mean my heart is fine?" Which response by the nurse is accurate?

   • A."Yes, a normal troponin rules out a heart attack."
   • B."Troponin only rises 2 weeks after heart damage."
   • C."A normal troponin means your pain is from anxiety."
   • D."Troponin can take a few hours to rise, so the test will be repeated."
   Show answer and explanation

   Answer: D

   Troponin is released when heart muscle cells are damaged. It begins to rise within a few hours of injury, so a single early value can be normal. Serial troponins, along with the ECG and symptoms, are used to diagnose or rule out a heart attack.

   • A. A single early troponin cannot rule out a heart attack. Levels may not have risen yet.
   • B. Troponin rises within hours, not weeks, and stays high for 1 to 2 weeks.
   • C. A normal result does not identify the cause of chest pain.
   • D. Correct. Troponin is checked again over the next hours to look for a rise that shows heart muscle damage.

   Key concept: Troponin is the preferred marker of heart muscle injury; serial values are needed.

   Tip: One troponin is a snapshot; the trend tells the story.