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Lab Values NCLEX practice questions
NCLEX lab questions test what a value means for the client and what you do about it. Items that include a numeric lab value also show the normal range, so focus on high versus low, the signs that go with each, and the priority action.
Question 1 · Physiological Adaptation
The nurse is caring for a client with type 1 diabetes who reports feeling shaky and diaphoretic. Fingerstick glucose is 58 mg/dL. What is the nurse's priority action?
Show answer and rationale
Answer: B. A glucose of 58 mg/dL is below 70 mg/dL, the threshold for hypoglycemia, so it should be treated immediately with 15 g of fast-acting carbohydrate to prevent worsening neurologic symptoms. Calling the provider delays urgently needed treatment for a symptomatic client. Administering insulin would dangerously lower the glucose further and is contraindicated during hypoglycemia. Waiting an hour to recheck without treating first risks progression to severe hypoglycemia, seizures, or loss of consciousness.
Checked against: OpenStax Pharmacology for Nurses, 28.1
Question 2 · Pharmacological and Parenteral Therapies
The nurse is caring for a client on warfarin therapy. Which findings require immediate provider notification? Select all that apply.
Select all that apply.
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Answer: D, E. Warfarin therapy is monitored using INR, with a goal of 2-3; an INR of 5.2 is dangerously elevated and requires the nurse to hold the dose and anticipate vitamin K administration. Spontaneous gum bleeding is a sign of excessive anticoagulation and must be reported immediately. An INR of 2.5 is within the therapeutic goal range and does not require notification. aPTT is used to monitor heparin, not warfarin, so a normal aPTT of 32 seconds is not directly relevant here. A platelet count of 250,000/mm3 is within normal limits and not concerning.
Checked against: OpenStax Clinical Nursing Skills, 28.2; OpenStax Medical-Surgical Nursing, 38.2
Question 3 · Reduction of Risk Potential
A client has a calcium level of 7.6 mg/dL. Which assessment finding supports this lab value?
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Answer: C. A calcium level of 7.6 mg/dL is below the normal range of 8.5-10.5 mg/dL, indicating hypocalcemia, which causes neuromuscular irritability manifested by a positive Chvostek sign (facial twitching) and Trousseau sign. Diminished reflexes are more characteristic of hypermagnesemia, not hypocalcemia. Polyuria is associated with hypercalcemia, the opposite imbalance. Isolated bradycardia is not a hallmark sign of low calcium.
Checked against: OpenStax Medical-Surgical Nursing, 10.3
Question 4 · Reduction of Risk Potential
The nurse reviews a client's platelet count of 45,000/mm3. Which intervention is most appropriate?
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Answer: D. A platelet count under 50,000/mm3 requires bleeding precautions, including a soft-bristle toothbrush and electric razor to minimize trauma and bleeding risk. Neutropenic precautions relate to a low ANC, not a low platelet count, so a private room is not indicated for this finding. Potassium monitoring is unrelated to thrombocytopenia. Fluid restriction has no role in bleeding precautions.
Checked against: OpenStax Medical-Surgical Nursing, 16.4; OpenStax Medical-Surgical Nursing, 16.5
Question 5 · Pharmacological and Parenteral Therapies
A client taking lithium for bipolar disorder reports new-onset coarse hand tremors, vomiting, and confusion. The lithium level is 1.8 mEq/L. What is the nurse's priority action?
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Answer: D. The lithium level of 1.8 mEq/L is above the toxic threshold of 1.5 mEq/L, and along with the symptoms of tremor, vomiting, and confusion, this confirms lithium toxicity, so the dose should be held and the provider notified immediately. Administering the next dose would worsen an already toxic level. Fluid and sodium should be maintained steady, not restricted, because dehydration and low sodium increase lithium reabsorption and worsen toxicity. Restricting sodium is the opposite of the correct action for lithium safety.
Checked against: OpenStax Pharmacology for Nurses, 13.3; OpenStax Psychiatric-Mental Health Nursing, 16.4
Question 6 · Pharmacological and Parenteral Therapies
A client taking phenytoin for seizure control has a level of 26 mcg/mL. Which findings should the nurse expect to assess? Select all that apply.
Select all that apply.
Show answer and rationale
Answer: A, D, E, F. A phenytoin level of 26 mcg/mL exceeds the therapeutic range of 10-20 mcg/mL, indicating toxicity, and classic signs include nystagmus, ataxia, slurred speech, and diplopia due to central nervous system depression. Hypertension is not a characteristic finding of phenytoin toxicity. Hyperactivity is inconsistent with the CNS-depressant effects of toxic phenytoin, which more typically causes sedation and impaired coordination.
Checked against: OpenStax Pharmacology for Nurses, 12.1
Question 7 · Physiological Adaptation
The nurse is caring for a client with hepatic encephalopathy and worsening confusion. Which laboratory value is most important for the nurse to trend?
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Answer: A. Rising ammonia levels in liver failure directly correlate with worsening confusion progressing toward coma, making ammonia the key value to trend in hepatic encephalopathy. Creatinine reflects renal, not hepatic, function. BUN can be elevated due to dehydration, GI bleeding, or steroid use and does not specifically reflect encephalopathy progression. Platelet count may be low in liver disease due to portal hypertension and splenic sequestration, but it does not correlate with mental status changes the way ammonia does.
Checked against: OpenStax Medical-Surgical Nursing, 19.6
Question 8 · Safety and Infection Control
A client with an absolute neutrophil count (ANC) of 800/mm3 develops a temperature of 100.6°F (38.1°C). What is the nurse's priority interpretation?
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Answer: A. In neutropenia, the first sign of infection may be only a low-grade fever, and this must be treated as an emergency because the client lacks the neutrophils needed to mount a robust immune response. Dismissing this fever as insignificant could delay life-saving treatment. Fresh flowers should actually be kept out of the room because they harbor bacteria and fungi that are dangerous to a neutropenic client, and fresh fruit and raw produce are kept off the tray because they can carry organisms. Neutropenic (reverse) isolation precautions are required, not avoided, when the ANC is under 1,000/mm3.
Checked against: OpenStax Medical-Surgical Nursing, 31.3; OpenStax Medical-Surgical Nursing, 16.5
Question 9 · Physiological Adaptation
A client receiving magnesium sulfate for preeclampsia has a magnesium level of 9.5 mEq/L (normal 1.3-2.1 mEq/L). Which assessment finding is most concerning?
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Answer: B. A magnesium level of 9.5 mEq/L is severely elevated, and high magnesium causes loss of deep tendon reflexes, respiratory depression, and cardiac arrhythmias, making absent reflexes an urgent finding requiring the nurse to stop the infusion. Reflexes of 2+ are normal and would not indicate toxicity. Muscle tremors and hyperactive reflexes are findings seen with low magnesium, not the toxic hypermagnesemia described here. This inverse presentation is a key testing point on magnesium physiology.
Checked against: OpenStax Maternal-Newborn Nursing, 12.2; OpenStax Medical-Surgical Nursing, 10.3
Question 10 · Management of Care
Prioritize hypotheses: The nurse is reviewing morning labs for an assigned group of clients. Which results should be reported to the provider before other routine tasks are completed? Select all that apply.
Select all that apply.
Show answer and rationale
Answer: A, C, E. Potassium abnormalities outrank other findings because they can stop the heart, and 6.5 mEq/L with ECG changes is a true emergency requiring immediate reporting. A lithium level of 1.9 mEq/L is toxic (above 1.5 mEq/L) with symptomatic coarse tremor, requiring the dose to be held and the provider notified. A low ANC with even a low-grade fever must be treated as a possible infectious emergency and reported immediately. An INR of 2.4 is within the therapeutic goal of 2-3 and needs no urgent report. Normal creatinine and BUN values reflect stable renal function and require no immediate action.
Checked against: OpenStax Clinical Nursing Skills, 28.2
Question 11 · Pharmacological and Parenteral Therapies
A client taking digoxin for heart failure reports nausea and seeing yellow-green halos around lights. The digoxin level is 2.4 ng/mL. What is the nurse's priority action?
Show answer and rationale
Answer: B. A digoxin level of 2.4 ng/mL exceeds the therapeutic range of 0.5-2.0 ng/mL, and yellow-green visual halos with nausea are classic signs of digoxin toxicity. The nurse should hold the dose, notify the provider, and check the potassium level because low potassium increases digoxin toxicity; DigiFab is used for life-threatening toxicity. Administering the next dose would worsen toxicity and is unsafe. These symptoms are not normal and should never be dismissed as expected. Simply increasing fluids and waiting 24 hours delays necessary intervention for a toxic level.
Checked against: OpenStax Pharmacology for Nurses, 19.6; OpenStax Clinical Nursing Skills, 11.1
Question 12 · Reduction of Risk Potential
A client's GFR has been 55 mL/min for the past 4 months. The nurse understands this finding is consistent with which condition?
Show answer and rationale
Answer: C. A GFR under 60 mL/min sustained for 3 months or longer meets the criteria for chronic kidney disease, unlike acute kidney injury, which develops suddenly rather than persisting over months. Normal GFR is 90 mL/min or greater, so 55 mL/min is well below normal. Prerenal azotemia from dehydration is typically a reversible, acute drop in renal perfusion rather than a sustained months-long reduction in GFR. The chronicity described in the stem is the key detail pointing to CKD.
Checked against: OpenStax Pharmacology for Nurses, 33.2; OpenStax Nutrition for Nurses, 16.1
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Frequently asked questions
Do you have to memorize lab values for the NCLEX?
NCLEX items that include a numeric lab value show the normal reference range. You still need to know what high and low mean, the signs that go with them and the priority action, which is what these questions practice.
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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.