NCLEX lab values cheat sheet
Every lab value tested on the NCLEX-RN with normal range, critical value, and the priority nursing action when it's abnormal. Bookmark this page, screenshot it, share it. Updated to the 2026 NCSBN test plan.
Complete Blood Count (CBC)
| Test | Normal range | Critical | Priority nursing action |
|---|---|---|---|
| WBC | 4,500–11,000/mm³ | <2,500 or >30,000 | Low: neutropenic precautions. High: rule out infection vs steroid response. |
| RBC | 4.2–6.1 million/mm³ | — | Low: bleeding, anemia, B12/folate deficiency. |
| Hemoglobin | M 13.5–17.5, F 12–15.5 g/dL | <7 | <7 transfuse symptomatic patients; assess for blood loss, fatigue, dyspnea. |
| Hematocrit | M 41–53%, F 36–46% | — | Roughly 3× hemoglobin. Low = anemia, dilution. High = dehydration, polycythemia. |
| Platelets | 150,000–450,000/mm³ | <50,000 or >1,000,000 | <50k bleeding precautions, no IM injections. <20k spontaneous bleeding risk. |
Basic Metabolic Panel (BMP)
| Test | Normal range | Critical | Priority nursing action |
|---|---|---|---|
| Sodium (Na+) | 135–145 mEq/L | <120 or >160 | Hyponatremia: seizure risk. Correct slowly to avoid central pontine myelinolysis. |
| Potassium (K+) | 3.5–5.0 mEq/L | <2.5 or >6.5 | Peaked T waves on EKG = hyperkalemia. <3.0 = digoxin toxicity risk. |
| Chloride (Cl-) | 98–106 mEq/L | — | Tracks with sodium and acid-base status. |
| CO2 (bicarb) | 22–28 mEq/L | — | <22 metabolic acidosis. >28 metabolic alkalosis or compensation. |
| BUN | 7–20 mg/dL | — | Elevated: dehydration, GI bleed, AKI, high-protein diet. |
| Creatinine | 0.6–1.2 mg/dL | >4.0 | Renal function marker. Hold metformin and adjust nephrotoxic drugs if elevated. |
| BUN:Cr ratio | 10:1 to 20:1 | — | >20:1 suggests prerenal cause (dehydration, GI bleed). |
| Glucose (fasting) | 70–100 mg/dL | <40 or >500 | <70 treat hypoglycemia. >250 with ketones = DKA workup. |
| Calcium (total) | 8.5–10.5 mg/dL | <7 or >13 | Hypocalcemia: Trousseau and Chvostek signs, seizure risk. |
| Magnesium | 1.5–2.5 mg/dL | — | Low: tetany, torsades de pointes. High: hyporeflexia, respiratory depression. |
| Phosphorus | 2.5–4.5 mg/dL | — | Inversely related to calcium. Refeeding syndrome risk. |
Arterial Blood Gas (ABG)
| Test | Normal range | Critical | Priority nursing action |
|---|---|---|---|
| pH | 7.35–7.45 | <7.20 or >7.60 | <7.35 acidosis. >7.45 alkalosis. Drives the entire interpretation. |
| PaCO2 | 35–45 mmHg | — | Respiratory parameter. >45 respiratory acidosis, <35 respiratory alkalosis. |
| HCO3- | 22–26 mEq/L | — | Metabolic parameter. <22 metabolic acidosis, >26 metabolic alkalosis. |
| PaO2 | 80–100 mmHg | <60 | <60 mmHg = respiratory failure. Increase FiO2 or escalate. |
| SaO2 | 95–100% | <88% | <88% requires intervention. <92% in non-COPD is concerning. |
Coagulation
| Test | Normal range | Critical | Priority nursing action |
|---|---|---|---|
| PT | 11–13 seconds | — | Extrinsic pathway. Affected by warfarin and liver disease. |
| INR (untreated) | 0.8–1.2 | >5 | Therapeutic on warfarin 2–3 (most), 2.5–3.5 (mechanical valve). >5 risk of bleeding. |
| aPTT | 30–40 seconds | — | Intrinsic pathway. Therapeutic on heparin 60–80 (1.5–2.5× baseline). |
| D-dimer | <500 ng/mL FEU | — | Elevated in PE, DVT, DIC. Rule-out test for thromboembolism. |
Cardiac markers
| Test | Normal range | Critical | Priority nursing action |
|---|---|---|---|
| Troponin I | <0.04 ng/mL | — | >0.04 myocardial injury. Rises 3–4 hr post-MI, peaks 24 hr, persists 1–2 weeks. |
| CK-MB | 0–3% of total CK | — | Rises 4–6 hr post-MI. Less specific than troponin. |
| BNP | <100 pg/mL | — | >400 heart failure likely. >900 severe HF. Use to assess volume status. |
Liver function
| Test | Normal range | Critical | Priority nursing action |
|---|---|---|---|
| ALT (SGPT) | 7–56 U/L | — | Liver-specific. Elevated in hepatitis, fatty liver, acetaminophen toxicity. |
| AST (SGOT) | 10–40 U/L | — | Less liver-specific. Also elevated in muscle injury, MI. |
| Alkaline phosphatase | 44–147 U/L | — | Elevated in cholestasis, bone disease, pregnancy. |
| Total bilirubin | 0.1–1.2 mg/dL | — | >2.5 visible jaundice. Indirect = hemolysis, direct = obstruction. |
| Albumin | 3.5–5.0 g/dL | — | Low: malnutrition, liver disease, nephrotic syndrome. |
Lipid panel (fasting)
| Test | Normal range | Critical | Priority nursing action |
|---|---|---|---|
| Total cholesterol | <200 mg/dL | — | >240 = high. Lifestyle + statin discussion. |
| LDL | <100 mg/dL | — | <70 for high cardiovascular risk patients. |
| HDL | M >40, F >50 mg/dL | — | Higher is better. Exercise raises HDL. |
| Triglycerides | <150 mg/dL | — | >500 acute pancreatitis risk. |
Therapeutic drug levels
| Test | Normal range | Critical | Priority nursing action |
|---|---|---|---|
| Digoxin | 0.5–2.0 ng/mL | — | Toxicity: nausea, vision changes, dysrhythmias, especially with low K+. |
| Lithium | 0.6–1.2 mEq/L | >1.5 | Narrow therapeutic window. Toxicity: tremor, confusion, seizure. |
| Phenytoin (Dilantin) | 10–20 mcg/mL | — | Toxicity: nystagmus, ataxia, gingival hyperplasia. |
| Vancomycin trough | 10–20 mcg/mL | — | Draw 30 min before next dose. Nephrotoxic and ototoxic. |
| Acetaminophen | <25 mcg/mL (4 hr post) | — | >150 at 4 hr = N-acetylcysteine indicated. |
How NCLEX tests lab values
Lab value questions on the NCLEX rarely ask "what is the normal range?" They ask:
- Which lab change is the priority concern in this client?
- Which finding requires immediate provider notification?
- Which lab result would prompt the nurse to hold a medication?
- Which assessment finding is consistent with this lab abnormality?
Memorize the ranges, but practice applying them. The Clarity question bank includes 500+ lab-interpretation questions with full rationales and citation to Davis's Lab Tests and Lewis Med-Surg.
Practice lab interpretation with 5 free NCLEX-RN questions covering electrolyte emergencies, ABG analysis, and drug-level monitoring.
Try free lab + pharmacology questions →