NCLEX Lab Values Questions
Lab value questions test whether you can interpret diagnostic data and respond with the correct nursing action.
Lab value questions appear on every NCLEX-RN. You will be given a set of lab results and asked to identify the imbalance, choose the priority intervention, or predict a complication. Memorizing ranges alone is not enough — you must connect each abnormal value to a clinical picture and a nursing action. Our free lab values question bank drills the specific values and scenarios most tested.
The 25 Lab Values You Must Know Cold
Electrolytes: Na+ 135–145, K+ 3.5–5.0, Cl- 95–105, Ca2+ 8.5–10.5, Mg2+ 1.5–2.5, Phos 2.5–4.5. Renal: BUN 10–20, Creatinine 0.6–1.2, eGFR over 90. Glucose: fasting 70–110, HbA1c under 5.7% normal / under 7% target for diabetics. Hematology: Hgb 12–18, Hct 36–52%, Platelets 150,000–400,000, WBC 5,000–10,000, ANC over 1,500. Coagulation: PT 11–13, INR 0.8–1.1 (2.0–3.0 on warfarin), aPTT 25–35 (1.5–2.5x normal on heparin). Cardiac: Troponin under 0.04, BNP under 100. Liver: ALT 10–40, AST 10–40, Total bilirubin 0.3–1.0. Drug levels: Digoxin 0.5–2.0, Lithium 0.6–1.2, Phenytoin 10–20, Valproic acid 50–100.
Critical Values That Demand Immediate Action
Critical values require you to notify the provider immediately. Memorize these thresholds: K+ under 3.0 or over 5.5 (cardiac arrhythmia risk), Na+ under 125 (seizures), glucose under 70 (hypoglycemia) or over 250 with symptoms (DKA risk), platelets under 50,000 (bleeding), ANC under 500 (severe neutropenia, reverse isolation), Hgb under 7 (transfusion trigger in most cases), INR over 5 on warfarin (bleeding risk, hold dose), digoxin over 2.0 (toxicity), lithium over 1.5 (toxicity), pH under 7.30 or over 7.55 (severe acid-base imbalance). On any question showing one of these values, the priority action is either notify or intervene — not routine monitoring.
ABG Interpretation Made Simple
ROME method: Respiratory Opposite, Metabolic Equal. Look at pH — under 7.35 acidosis, over 7.45 alkalosis. Look at CO2 (35–45) and HCO3 (22–26). If pH and CO2 move in OPPOSITE directions, it is respiratory. If pH and HCO3 move in the SAME direction, it is metabolic. Then determine compensation: if the opposite value has changed to counteract the primary problem, the patient is partially or fully compensated. Common patterns: respiratory acidosis (COPD, opioid overdose, hypoventilation), respiratory alkalosis (anxiety, PE, salicylate toxicity early), metabolic acidosis (DKA, lactic acidosis, kidney failure), metabolic alkalosis (vomiting, diuretics, antacid overuse).
Drug-Level Monitoring Questions
Drug-level questions test whether you know when to hold a dose, when to notify the provider, and when to expect toxicity signs. Digoxin — hold for HR under 60 or level over 2.0, early toxicity is anorexia and visual halos, hypokalemia potentiates toxicity. Lithium — narrow range 0.6–1.2, over 1.5 causes tremor and ataxia, over 2.0 causes seizures. Warfarin — INR over 5 hold and administer vitamin K, INR under 2 subtherapeutic. Heparin — aPTT over 2.5x normal reduce infusion, protamine sulfate is the antidote. Vancomycin — trough 10–20, over 20 causes nephrotoxicity, monitor peak and trough, red-man syndrome from rapid infusion (not an allergy).
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