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NCLEX lab values cheat sheet
These are the reference ranges NCLEX questions are written around — commonly used adult values from standard nursing review sources. Learn the normal range, the panic direction (which way kills the client), and the nursing action tied to it. Print this page — it's print-styled.
Electrolytes
| Value | Normal | Remember |
|---|
| Sodium (Na⁺) | 135–145 mEq/L | Neuro changes both directions — seizures at extremes |
| Potassium (K⁺) | 3.5–5.0 mEq/L | The cardiac one. High or low → dysrhythmias; check EKG |
| Chloride (Cl⁻) | 95–105 mEq/L | Follows sodium |
| Calcium (Ca²⁺) | 9.0–10.5 mg/dL | Low → Chvostek/Trousseau, tetany; high → stones, groans |
| Magnesium (Mg²⁺) | 1.3–2.1 mEq/L | Low Mg often travels with low K⁺ and low Ca²⁺ |
| Phosphorus | 3.0–4.5 mg/dL | Inverse relationship with calcium |
Renal & glucose
| Value | Normal | Remember |
|---|
| BUN | 10–20 mg/dL | Rises with dehydration, not just kidney injury |
| Creatinine | 0.6–1.3 mg/dL | The kidney number. Trending up = renal impairment |
| Glucose (fasting) | 70–110 mg/dL | <70 = treat the hypoglycemia first |
| HbA1c (goal, diabetic) | <7% | 3-month average control |
CBC
| Value | Normal | Remember |
|---|
| Hemoglobin | M 14–18 · F 12–16 g/dL | Oxygen carrier — fatigue, pallor when low |
| Hematocrit | M 42–52% · F 37–47% | ≈ 3 × Hgb |
| WBC | 5,000–10,000 /mm³ | <5,000 → neutropenic precautions territory |
| Platelets | 150,000–400,000 /mm³ | <50,000 bleeding risk — soft toothbrush, no razors, fall precautions |
Coagulation
| Value | Normal | Remember |
|---|
| INR | 0.8–1.1 (therapeutic on warfarin: 2–3) | High INR → hold warfarin, vitamin K is the antidote |
| PT | 11–12.5 sec | Warfarin follows PT/INR |
| aPTT | 30–40 sec (therapeutic on heparin: 1.5–2×) | Heparin follows aPTT; protamine sulfate is the antidote |
ABGs
| Value | Normal | Remember |
|---|
| pH | 7.35–7.45 | <7.35 acidosis · >7.45 alkalosis |
| PaCO₂ | 35–45 mmHg | Respiratory driver — opposite direction to pH = respiratory cause |
| HCO₃⁻ | 22–26 mEq/L | Metabolic driver — same direction as pH = metabolic cause |
| PaO₂ | 80–100 mmHg | <80 = hypoxemia |
| SaO₂ | 95–100% | Know your client's baseline (COPD may live lower) |
ROME: Respiratory Opposite, Metabolic Equal — the fastest way to classify an ABG on exam day.
Liver
| Value | Normal | Remember |
|---|
| Albumin | 3.5–5.0 g/dL | Low → edema, poor wound healing |
| Total bilirubin | 0.3–1.0 mg/dL | High → jaundice |
| Ammonia | 10–80 mcg/dL | High → hepatic encephalopathy; lactulose brings it down |
| AST / ALT | ≈ 10–40 units/L | Elevated = hepatocellular injury |
Drug therapeutic levels
| Drug | Therapeutic | Remember |
|---|
| Digoxin | 0.5–2.0 ng/mL | Toxicity: nausea, vision changes, bradycardia — check apical pulse & K⁺ |
| Lithium | 0.6–1.2 mEq/L | >1.5 toxic — tremor, GI upset; keep sodium and fluids steady |
| Phenytoin | 10–20 mcg/mL | Toxicity: ataxia, nystagmus, gingival hyperplasia |
How to actually memorize these
- Learn ranges in pairs with consequences ("K⁺ 3.5–5.0 → outside it, think EKG"), not as bare numbers.
- Drill the critical ones daily: K⁺, Na⁺, platelets, INR, digoxin, lithium — they carry the most question weight.
- Practice in question form. The exam won't ask "what is normal potassium" — it gives you a value inside a scenario and asks what you do about it.
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