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Lab Values & Diagnostics Practice Test

These 25 questions test your ability to interpret laboratory results, identify critical values that require immediate provider notification, correlate abnormal findings with clinical conditions, and understand the nursing actions triggered by abnormal diagnostics.

~7%
Integrated across all body systemsof the NCLEX-RN exam
25 questions ~15 minutes Instant scoring No signup needed

Lab Values & Diagnostics Quiz

Test your NCLEX skills with these 25 lab value questions on ABG, electrolytes, CBC, and critical values with instant scoring.

25 questions | 90 minutes | 70% to pass

Question 1: A patient serum potassium level is 2.8 mEq/L. The nurse should be MOST concerned about the risk of:

  1. Increased urine output and thirst
  2. Elevated blood pressure and headache
  3. Constipation and abdominal bloating
  4. Life-threatening cardiac arrhythmias and muscle weakness

Answer: D — Normal potassium is 3.5 to 5.0 mEq/L. A level of 2.8 is critically low (hypokalemia) and can cause fatal cardiac arrhythmias (flattened T waves, U waves, ventricular fibrillation), skeletal muscle weakness, leg cramps, and paralytic ileus. Obtain a stat ECG and notify the provider.

Question 2: A patient serum sodium level is 118 mEq/L. The PRIORITY nursing action is:

  1. Implement seizure precautions and notify the provider immediately
  2. Administer IV normal saline at a rapid rate without orders
  3. Encourage the patient to drink more water
  4. Restrict dietary sodium intake

Answer: A — Normal sodium is 135 to 145 mEq/L. A level of 118 is severe hyponatremia causing cerebral edema, which can trigger seizures, coma, and death. Implement seizure precautions, perform neurological checks, notify the provider, and anticipate fluid restriction or cautious hypertonic saline administration.

Question 3: A patient serum calcium level is 6.2 mg/dL and they report tingling around the mouth and muscle cramps. The nurse should:

  1. Encourage the patient to increase dietary sodium
  2. Restrict the patient calcium intake further
  3. Recognize these as signs of hypocalcemia and notify the provider for IV calcium replacement
  4. Administer a calcium channel blocker to correct the imbalance

Answer: C — Normal calcium is 8.5 to 10.5 mg/dL. A level of 6.2 with perioral tingling and muscle cramps indicates symptomatic hypocalcemia. Check for Chvostek sign (facial twitching) and Trousseau sign (carpal spasm). Severe hypocalcemia causes tetany, laryngospasm, and cardiac arrest. IV calcium gluconate is the priority treatment.

Question 4: A patient with chronic kidney disease has a potassium level of 6.5 mEq/L. The nurse notes peaked T waves on the cardiac monitor. The FIRST intervention the nurse should anticipate is:

  1. Emergent dialysis to remove excess potassium
  2. IV calcium gluconate to stabilize the cardiac membrane
  3. Oral kayexalate to bind potassium in the gut
  4. IV insulin with glucose to shift potassium intracellularly

Answer: B — Peaked T waves with potassium of 6.5 indicate the heart is being affected by hyperkalemia. IV calcium gluconate is given FIRST because it stabilizes the cardiac membrane within minutes, protecting against fatal arrhythmias. Insulin with glucose and kayexalate work to lower potassium but take longer.

Question 5: A patient serum magnesium level is 1.0 mEq/L. The nurse should monitor for:

  1. Hypertension and fluid overload
  2. Weight gain and peripheral edema
  3. Excessive sedation and respiratory depression
  4. Tremors, hyperreflexia, and cardiac arrhythmias

Answer: D — Normal magnesium is 1.5 to 2.5 mEq/L. A level of 1.0 is hypomagnesemia, which causes neuromuscular excitability: tremors, hyperactive reflexes, muscle cramps, seizures, and cardiac arrhythmias (especially torsades de pointes). Low magnesium often accompanies hypokalemia and must be corrected for potassium replacement to be effective.

Question 6: A patient fasting blood glucose is 58 mg/dL. The patient is conscious, alert, and diaphoretic. The nurse should FIRST:

  1. Give 15 grams of a fast-acting oral carbohydrate such as 4 ounces of juice
  2. Recheck the glucose in one hour before intervening
  3. Hold all food and fluids and notify the provider
  4. Administer IV dextrose 50 percent immediately

Answer: A — Normal fasting glucose is 70 to 100 mg/dL. A level of 58 in a conscious patient is treated with the Rule of 15: give 15 grams of fast-acting carbohydrate, wait 15 minutes, recheck. IV dextrose is reserved for unconscious patients who cannot swallow safely.

Question 7: A patient blood glucose is 42 mg/dL and they are unconscious and unresponsive. The nurse should:

  1. Place orange juice in the patient mouth to raise the glucose
  2. Administer regular insulin to stabilize the glucose level
  3. Administer IV dextrose 50 percent (D50) or IM glucagon immediately
  4. Wait for the patient to regain consciousness before treating

Answer: C — An unconscious patient cannot safely swallow, so oral carbohydrates risk aspiration. IV D50 is the treatment of choice for severe hypoglycemia with altered consciousness. IM glucagon is an alternative if IV access is not available. Never give anything by mouth to an unconscious patient.

Question 8: A patient HbA1c result is 9.2 percent. The nurse interprets this as:

  1. An acute hypoglycemic episode requiring immediate treatment
  2. A normal result for a non-diabetic patient
  3. Well-controlled diabetes within the target range
  4. Poorly controlled diabetes indicating elevated blood glucose over the past 2 to 3 months

Answer: D — HbA1c reflects average blood glucose over the previous 2 to 3 months. Normal is below 5.7 percent, prediabetes is 5.7 to 6.4, diabetes is 6.5 or above. The ADA target for most diabetics is below 7 percent. A result of 9.2 indicates significant hyperglycemia and poor long-term glucose control.

Question 9: A patient ABG results show: pH 7.32, PaCO2 48 mmHg, HCO3 24 mEq/L. The nurse identifies this as:

  1. Metabolic alkalosis
  2. Respiratory acidosis
  3. Respiratory alkalosis
  4. Metabolic acidosis

Answer: B — pH 7.32 is acidotic (below 7.35). PaCO2 48 is elevated (above 45) causing the acidosis. HCO3 24 is normal (22-26) showing no renal compensation. This is uncompensated respiratory acidosis, commonly caused by COPD, hypoventilation, respiratory depression, or airway obstruction.

Question 10: A patient ABG shows: pH 7.50, PaCO2 28 mmHg, HCO3 23 mEq/L. This indicates:

  1. Metabolic acidosis
  2. Respiratory acidosis
  3. Metabolic alkalosis
  4. Respiratory alkalosis

Answer: D — pH 7.50 is alkalotic (above 7.45). PaCO2 28 is low (below 35) causing the alkalosis. HCO3 23 is normal. This is uncompensated respiratory alkalosis, typically caused by hyperventilation from anxiety, pain, fever, or early sepsis. Treatment: address the underlying cause and slow the breathing rate.

Question 11: A patient ABG results show: pH 7.28, PaCO2 36 mmHg, HCO3 16 mEq/L. The nurse identifies this as:

  1. Metabolic acidosis
  2. Respiratory acidosis
  3. Respiratory alkalosis
  4. Metabolic alkalosis

Answer: A — pH 7.28 is acidotic. PaCO2 36 is normal (35-45) so the lungs are not the primary cause. HCO3 16 is low (below 22) causing the acidosis. This is metabolic acidosis, commonly caused by diabetic ketoacidosis, renal failure, lactic acidosis, or severe diarrhea.

Question 12: A patient ABG results show: pH 7.48, PaCO2 40 mmHg, HCO3 32 mEq/L. This indicates:

  1. Metabolic alkalosis
  2. Respiratory alkalosis
  3. Metabolic acidosis
  4. Respiratory acidosis

Answer: A — pH 7.48 is alkalotic. PaCO2 40 is normal so the lungs are not the cause. HCO3 32 is elevated (above 26) causing the alkalosis. This is metabolic alkalosis, commonly caused by prolonged vomiting, NG suctioning, excessive antacid use, or diuretic therapy.

Question 13: A patient ABG shows: pH 7.33, PaCO2 55 mmHg, HCO3 30 mEq/L. The nurse interprets this as:

  1. Fully compensated metabolic alkalosis
  2. Partially compensated respiratory acidosis with renal compensation
  3. Uncompensated respiratory acidosis
  4. Uncompensated metabolic acidosis

Answer: B — pH 7.33 is still acidotic (not yet normalized). PaCO2 55 is elevated (respiratory acidosis). HCO3 30 is elevated (above 26) showing the kidneys are retaining bicarbonate to compensate. Since pH remains abnormal, this is partially compensated respiratory acidosis - common in chronic COPD.

Question 14: A patient with COPD has the ABG: pH 7.37, PaCO2 58 mmHg, HCO3 33 mEq/L. This represents:

  1. Uncompensated metabolic alkalosis
  2. Normal ABG values requiring no intervention
  3. Fully compensated respiratory acidosis consistent with chronic COPD
  4. An acute respiratory emergency requiring intubation

Answer: C — pH 7.37 is within normal range (7.35-7.45) despite elevated PaCO2 (chronic CO2 retention in COPD). The elevated HCO3 shows complete renal compensation. This is the expected baseline for a chronic COPD patient. The kidneys have had time to fully compensate by retaining bicarbonate.

Question 15: A patient hemoglobin is 7.2 g/dL and hematocrit is 22 percent. The patient reports fatigue and dyspnea on exertion. The nurse should:

  1. Encourage increased oral fluid intake to dilute the blood
  2. Notify the provider immediately and anticipate a blood transfusion order
  3. Administer supplemental iron tablets and discharge the patient
  4. Schedule a follow-up appointment for next month

Answer: B — Normal hemoglobin is 12-16 g/dL (female) and 14-18 g/dL (male). A level of 7.2 with symptoms (fatigue, exertional dyspnea) indicates severe anemia likely requiring transfusion. Hematocrit of 22 percent (normal 36-46 female, 42-52 male) confirms significant red blood cell deficit.

Question 16: A patient WBC count is 1,800 cells/mcL. The nurse should PRIORITIZE which intervention?

  1. Implementing neutropenic precautions including strict hand hygiene, avoiding fresh flowers and raw foods, and limiting visitors with infections
  2. Encouraging vigorous exercise to stimulate white cell production
  3. No intervention is needed since this is within normal range
  4. Administering antibiotics prophylactically without a provider order

Answer: A — Normal WBC is 4,500 to 11,000 cells/mcL. A count of 1,800 indicates severe leukopenia (neutropenia), leaving the patient extremely vulnerable to infection. Implement protective isolation: strict hand hygiene, no fresh flowers or fruits, no sick visitors, monitor temperature closely, and report any fever immediately.

Question 17: A patient platelet count is 18,000/mcL. Which nursing intervention is MOST important?

  1. Encouraging the patient to ambulate vigorously to improve circulation
  2. Implementing bleeding precautions: soft toothbrush, electric razor, avoid IM injections, and monitor for bleeding
  3. No special precautions are needed at this platelet level
  4. Administering aspirin for headache as requested by the patient

Answer: B — Normal platelets are 150,000 to 400,000/mcL. A count of 18,000 is severely low (thrombocytopenia) with high spontaneous bleeding risk. Implement bleeding precautions: soft toothbrush, electric razor, no IM injections, avoid rectal temperatures, apply prolonged pressure to venipuncture sites, and monitor for petechiae and bleeding.

Question 18: A patient on chemotherapy has the following CBC: WBC 2,100, hemoglobin 8.5, platelets 45,000. Which finding presents the MOST immediate life-threatening risk?

  1. The low platelet count increasing bleeding risk
  2. The low hemoglobin causing fatigue
  3. The low WBC count increasing infection risk which is the leading cause of death in neutropenic patients
  4. All three are equally urgent

Answer: C — While all values are abnormal, neutropenia (WBC 2,100) poses the most immediate life-threatening risk because infection in an immunocompromised patient can rapidly progress to sepsis and death within hours. Even a low-grade fever in a neutropenic patient is a medical emergency requiring immediate blood cultures and antibiotics.

Question 19: A patient hematocrit is 58 percent. The nurse should be concerned about the risk of:

  1. Bleeding and hemorrhage
  2. Blood clot formation, stroke, and impaired circulation due to increased blood viscosity
  3. Immunosuppression and infection risk
  4. Severe anemia requiring transfusion

Answer: B — Normal hematocrit is 36-46 percent (female) and 42-52 percent (male). A level of 58 indicates polycythemia - excessive red blood cells making the blood thick and viscous. This dramatically increases the risk of blood clots, stroke, and myocardial infarction due to sluggish blood flow.

Question 20: A patient with a history of blood clots has been started on heparin. The nurse should assess the following lab values:

  1. Serum potassium and sodium levels
  2. PT/INR to monitor the heparin effectiveness
  3. Hemoglobin and hematocrit only
  4. aPTT (activated partial thromboplastin time) and platelet count

Answer: D — Heparin is monitored with aPTT (therapeutic range: 1.5 to 2.5 times control, approximately 46-70 seconds). Platelet count must also be monitored because heparin-induced thrombocytopenia (HIT) is a serious complication. PT/INR monitors warfarin, not heparin. Knowing which lab matches which anticoagulant is critical.

Question 21: A patient on warfarin has a PT of 28 seconds and an INR of 3.8. The nurse should:

  1. Increase the warfarin dose to achieve stronger anticoagulation
  2. Administer the next warfarin dose as scheduled since the patient needs anticoagulation
  3. Hold the warfarin, notify the provider, and assess for signs of bleeding
  4. Administer heparin to supplement the warfarin

Answer: C — Therapeutic INR for warfarin is 2.0 to 3.0. An INR of 3.8 is supratherapeutic, indicating excessive anticoagulation with increased bleeding risk. Hold the dose, notify the provider (who may order vitamin K), and assess for bleeding: bruising, hematuria, melena, gum bleeding, and neurological changes.

Question 22: A patient presents to the ED with crushing chest pain. The troponin I level returns at 4.2 ng/mL (normal less than 0.04). The nurse interprets this as:

  1. An elevated liver enzyme indicating hepatic damage
  2. A normal finding in a patient with chest pain
  3. Strong evidence of acute myocardial damage consistent with myocardial infarction
  4. A marker of kidney function decline

Answer: C — Troponin is the most specific and sensitive biomarker for cardiac muscle damage. A troponin of 4.2 (normal below 0.04) confirms significant myocardial injury. Combined with chest pain, this strongly indicates acute MI requiring emergent cardiac intervention (catheterization and reperfusion).

Question 23: A patient BNP level is 1,250 pg/mL. The nurse should assess for:

  1. Signs of pulmonary embolism such as pleuritic chest pain
  2. Signs of liver failure such as jaundice and ascites
  3. Signs of acute kidney injury such as oliguria
  4. Signs and symptoms of heart failure: dyspnea, crackles, peripheral edema, weight gain, and jugular vein distention

Answer: D — BNP (B-type natriuretic peptide) is released by the ventricles when they are stretched from volume overload. Normal is below 100 pg/mL. A level of 1,250 strongly indicates heart failure. Assess for dyspnea, orthopnea, crackles, edema, weight gain, and elevated JVP.

Question 24: A patient BUN is 42 mg/dL and creatinine is 3.8 mg/dL. These results MOST likely indicate:

  1. Impaired kidney function with reduced ability to filter waste products
  2. Dehydration that will resolve with oral fluid intake alone
  3. Normal kidney function in a healthy adult
  4. Liver failure causing accumulation of toxins

Answer: A — Normal BUN is 7 to 20 mg/dL and creatinine is 0.6 to 1.2 mg/dL. Both are markedly elevated, indicating the kidneys are failing to adequately filter waste products (azotemia). Creatinine is the more specific marker for kidney function. Assess urine output, fluid balance, and notify the provider.

Question 25: A patient on heparin therapy has the following result: platelet count dropped from 220,000 to 82,000 over 5 days. The nurse should suspect:

  1. Heparin-induced thrombocytopenia (HIT) requiring immediate discontinuation of all heparin products
  2. The patient is not receiving enough heparin and the dose should be increased
  3. Normal platelet variation that requires no intervention
  4. A lab error that should be repeated next week

Answer: A — A platelet drop of more than 50 percent within 5 to 10 days of starting heparin strongly suggests HIT - a serious immune-mediated reaction that paradoxically causes life-threatening blood clots despite low platelets. Stop ALL heparin products immediately, notify the provider, and anticipate switching to a direct thrombin inhibitor.

What your score means

85% or above — Strong lab interpretation skills

You can identify critical values, correlate them with clinical conditions, and select appropriate nursing actions. These skills improve your performance across every other NCLEX-RN category.

70–84% — Close. Drill your critical value thresholds.

Most students in this range know the normal ranges but miss the critical threshold or the correct nursing action. Use the gauge reference below — focus on what triggers provider notification and what the first action is.

Below 70% — Work through every gauge panel.

Lab questions appear embedded across every category — a weak score here affects your whole exam. Work systematically through the spectrum gauges and critical value grids, then retake before your exam date.

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What’s covered in Lab Values & Diagnostics

This category tests whether you know normal ranges, can identify critical values, understand what abnormal results mean clinically, and know what the nurse does first when a result falls outside the safe range.

Electrolytes & Metabolic

Sodium, potassium, calcium, magnesium, glucose — normal ranges, critical thresholds, and conditions that cause each imbalance.

~8 questions

ABG Interpretation

pH, PaCO₂, HCO₃, PaO₂ — recognising the four acid-base disorders, compensation states, and clinical conditions associated with each.

~6 questions

Haematology

CBC components, haemoglobin, haematocrit, WBC, platelets — what each value tells you and when it requires immediate action.

~6 questions

Coagulation & Cardiac Markers

PT/INR, aPTT, troponin, BNP, creatinine, BUN — therapeutic ranges, monitoring parameters, and clinical implications.

~5 questions

All NCLEX-RN practice topics

Safe & Effective Care
25 questions — 21–33%
Pharmacology & Parenteral
25 questions — 12–18%
Physiological Adaptation
25 questions — 11–17%
Reduction of Risk
25 questions — 9–15%
Health Promotion
25 questions — 6–12%
Psychosocial Integrity
25 questions — 6–12%
Mental Health
25 questions
Maternal & Newborn
25 questions
Pediatric Nursing
25 questions
You are here
Lab Values & Diagnostics
25 questions
Full 75-Question Test
All categories · Exam conditions

How to master Lab Values & Diagnostics

Learn critical values separately from normal ranges

Knowing that normal potassium is 3.5–5.0 mEq/L is not enough. You also need to know that below 2.5 or above 6.5 is a critical value requiring immediate provider notification. The NCLEX tests both: what is normal, AND what crosses the threshold that demands immediate action. These are two different facts — study them together for every key lab.

Master ABG interpretation with the ROME mnemonic

Respiratory Opposite, Metabolic Equal. In respiratory disorders, pH and PaCO₂ move in opposite directions. In metabolic disorders, pH and HCO₃ move in the same direction. Practise applying this to four base scenarios until it takes you under 10 seconds to identify the disorder type. ABG interpretation questions appear frequently and are completely predictable once the pattern is learned.

Correlate each abnormal value with its clinical condition

The NCLEX rarely asks “what is the normal range for X?” in isolation. It gives you a patient with a condition and asks what lab value you expect, or gives you a lab value and asks what it indicates clinically. Know the pairs: loop diuretics cause hypokalemia, renal failure causes hyperkalemia, SIADH causes hyponatremia, DKA causes metabolic acidosis. These clinical correlations are the questions.

Know the nursing action for every critical value, not just the value itself

A potassium of 2.4 mEq/L requires you to assess the patient, hold any digoxin, notify the provider, and prepare for oral or IV potassium replacement. A platelet count of 30,000 requires bleeding precautions and provider notification. The NCLEX tests what you do, not just what the value means. Every critical value has a paired nursing response — study them together.

Retake until you score 85%+ consistently

Lab value questions are among the most learnable on the NCLEX because the content is finite and the correct answers follow a consistent clinical logic. Each wrong answer points to a specific value or clinical correlation to review. Use the spectrum gauges below after each retake.

Quick Reference Cheat Sheets

Three formats: spectrum gauges showing normal zones and danger thresholds, an ABG interpretation grid, and critical value panels by system — everything you need to scan before your exam.

Electrolyte & Key Lab Spectrum Gauges
Each gauge shows the normal zone in green and the danger zones in red. The right column shows nursing actions at abnormal values.
Potassium (K⁺)
mEq/L
Electrolyte
Normal: 3.5–5.0 mEq/L
Critical <2.5 Low <3.5 3.5–5.0 High >5.0 Critical >6.5
Hypo: Assess ECG (flat T-waves), hold digoxin, notify provider, K⁺ replacement — never IV push
Hyper: Peaked T-waves, cardiac monitor, calcium gluconate first (cardiac protection), restrict K⁺
Sodium (Na⁺)
mEq/L
Electrolyte
Normal: 136–145 mEq/L
Critical <120 Low <136 136–145 High >145 Critical >160
Hypo: Seizure precautions, fluid restriction (SIADH), correct Na⁺ slowly — rapid correction causes osmotic demyelination
Hyper: Free water deficit, neurological changes, hypotonic IV fluids, neuro checks
Calcium (Ca²⁺)
mg/dL
Electrolyte
Normal: 8.5–10.5 mg/dL
Critical <6 Low <8.5 8.5–10.5 High >10.5 Critical >13
Hypo: Trousseau’s & Chvostek’s signs, tetany, seizure precautions, IV calcium gluconate (NOT chloride peripherally)
Hyper: “Bones, stones, groans, moans” — pathological fractures, renal stones, N/V, confusion; IV fluids, loop diuretics
Glucose (fasting)
mg/dL
Metabolic
Normal: 70–100 mg/dL (fasting)
Critical <40 Low <70 70–100 High >126 Critical >500
Hypo (<70): 15g fast carbs if conscious; D50W IV or glucagon IM if unconscious; recheck in 15 min (15/15 rule)
DKA (>300): IV NS first, then Regular insulin infusion (after K⁺ confirmed >3.5), monitor K⁺ closely
Haemoglobin
g/dL
Haematology
Normal: 12–16 (F) • 14–18 (M) g/dL
Critical <7 Low <12 12–18 Polycythaemia >18 Critical >20
Critical low <7: Notify provider, prepare for transfusion, O₂, activity restriction, monitor for tachycardia and dyspnoea
Verify with two nurses at bedside before transfusion; blood must infuse within 4 hours per unit; use only NS
Platelets
/µL
Haematology
Normal: 150,000–400,000 /µL
Critical <50k Low <150k 150k–400k High >400k Critical >1M
Thrombocytopenia <50k: Bleeding precautions (soft toothbrush, no IM, no rectal temps, electric razor), notify provider, avoid ASA/NSAIDs
Heparin-induced thrombocytopenia (HIT): If platelets drop >50% on days 5–10 of heparin → stop heparin immediately
INR (Warfarin)
ratio
Coagulation
Therapeutic: 2.0–3.0 (A-fib / DVT) • 2.5–3.5 (mechanical valve)
Sub-therapeutic <2.0 2.0–3.0 Supratherapeutic >3.0 Critical >4.0
INR >4.0: Hold warfarin, notify provider, assess for bleeding, administer Vitamin K (phytonadione) if ordered
Sub-therapeutic: Risk of clot; dose adjustment needed; consistent Vitamin K dietary intake
Creatinine
mg/dL
Renal
Normal: 0.6–1.2 mg/dL
0.6–1.2 Mild elevation 1.3–3.0 Severe >3.0 Critical >10
Elevated: Monitor urine output (<30 mL/hr = notify), hold nephrotoxic medications (NSAIDs, ACE inhibitors, contrast dye), notify provider
Best single indicator of renal function. Rising creatinine + falling UO = acute kidney injury until proven otherwise
ABG Interpretation — ROME Method
Normal ABG Values
pH
7.35–7.45
Critical <7.20 or >7.60
PaCO₂
35–45 mmHg
Critical >70 mmHg
HCO₃
22–26 mEq/L
Metabolic indicator
PaO₂
80–100 mmHg
Critical <60 mmHg
SpO₂
≥95%
COPD target: 88–92%
ROME: Four Disorder Types
Resp. Acidosis
pH ↓   PaCO₂ ↑   HCO₃ normal
COPD, opioids, sedation
Resp. Alkalosis
pH ↑   PaCO₂ ↓   HCO₃ normal
Hyperventilation, anxiety, PE
Metab. Acidosis
pH ↓   PaCO₂ normal   HCO₃ ↓
DKA, renal failure, diarrhoea
Metab. Alkalosis
pH ↑   PaCO₂ normal   HCO₃ ↑
Vomiting, loop diuretics, NGT suction
ROME mnemonic
Respiratory Opposite • Metabolic Equal
Key to memorise
Critical Values Requiring Immediate Provider Notification
Electrolytes
Potassium<2.5 or >6.5 mEq/L
Sodium<120 or >160 mEq/L
Calcium<6 or >13 mg/dL
Magnesium<1.0 or >4.9 mEq/L
Glucose<40 or >500 mg/dL
Haematology
Haemoglobin<7 g/dL
Haematocrit<21% or >65%
Platelets<50,000 /µL
WBC<2,000 or >30,000 /µL
INR>4.0 (hold warfarin)
ABG & Respiratory
pH<7.20 or >7.60
PaCO₂>70 mmHg
PaO₂<60 mmHg
SpO₂<90% (notify)
Cardiac & Renal
TroponinAny elevation = notify
Digoxin level>2.0 ng/mL = toxic
Lithium level>1.5 mEq/L = toxic
Creatinine>10 mg/dL (critical)
Urine output<30 mL/hr for 2+ hrs
Full test
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Frequently asked questions

What is the most important potassium fact to know for the NCLEX-RN?
Know two things: the critical threshold (<2.5 or >6.5 mEq/L requires immediate provider notification), and that IV potassium is never given as an IV push — it must be diluted and infused slowly, max 10 mEq/hr peripherally. Rapid IV potassium can cause fatal cardiac arrhythmias. Also: hypokalemia increases digoxin toxicity risk, so always check potassium before administering digoxin.
How do I apply the ROME mnemonic for ABG interpretation?
ROME stands for Respiratory Opposite, Metabolic Equal. In respiratory disorders, pH and PaCO₂ move in opposite directions: respiratory acidosis has low pH and high PaCO₂; respiratory alkalosis has high pH and low PaCO₂. In metabolic disorders, pH and HCO₃ move in the same direction: metabolic acidosis has low pH and low HCO₃; metabolic alkalosis has high pH and high HCO₃. Start with pH, then identify whether PaCO₂ or HCO₃ explains the change.
What is the significance of an elevated troponin level?
Any elevation in troponin (troponin I or troponin T) above the reference range is a critical finding that requires immediate provider notification. Troponin is the most sensitive and specific biomarker for myocardial injury — it rises within 3–4 hours of MI onset, peaks at 12–24 hours, and remains elevated for 7–10 days. Unlike CK-MB, troponin has no normal elevation threshold; any detectable level above baseline is clinically significant.
Why does hypokalemia increase the risk of digoxin toxicity?
Digoxin and potassium compete for the same binding site on the Na-K-ATPase pump. When serum potassium is low, digoxin binds more readily to the pump, effectively increasing its concentration at the receptor site even when the serum digoxin level appears within the therapeutic range. This is why the NCLEX frequently pairs digoxin administration with a potassium check — and why hypokalemia from loop diuretics (furosemide) is a significant safety concern in patients taking digoxin.
Can I take this quiz more than once?
Yes, unlimited retakes with no signup required. For Lab Values specifically, review the gauge panel for each value you missed, then retake. The critical threshold and the nursing action for each value are the two facts most likely to appear in a question — make sure you know both for every lab in the spectrum above.

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All spectrum gauges, critical value thresholds, ABG interpretation grid, and the ROME mnemonic — one printable page for exam day.

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