NCLEX Lab Values Cheat Sheet: The Numbers Worth Memorizing

These are the reference ranges NCLEX questions are written around — commonly used adult values from standard nursing review sources. For each one, learn the normal range, the panic direction (which way harms the client), and the nursing action tied to it. This page is print-styled — print it.

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
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⁺

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 (diabetic goal)	<7%	3-month average control

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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 (warfarin: 2–3)	High INR → hold warfarin; vitamin K is the antidote
aPTT	30–40 sec (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 to pH = respiratory cause
HCO₃⁻	22–26 mEq/L	Metabolic driver — same direction as pH = metabolic cause
PaO₂	80–100 mmHg	<80 = hypoxemia

ROME: Respiratory Opposite, Metabolic Equal — the fastest way to classify an ABG on exam day.

Therapeutic drug 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

Don't drill numbers in a vacuum — attach each to the action it triggers (low K⁺ → hold digoxin, check EKG). CinnaRN turns every value into a swipeable card with its nursing action and shows it inside real questions, so the number sticks because you used it. Browse the free cheat-sheet library or practice in the app.