NCLEX Lab Values Cheat Sheet

Lab values are guaranteed to appear on the NCLEX. You need to know normal ranges, what abnormal values indicate, and the nursing actions to take. Here's your complete cheat sheet.

Complete Blood Count (CBC)

Lab Value	Normal Range	Low =	High =
WBC	5,000–10,000/mm³	Infection risk	Infection/inflammation
RBC	M: 4.7–6.1 M/mm³	Anemia	Polycythemia
	F: 4.2–5.4 M/mm³
Hemoglobin	M: 14–18 g/dL	Anemia, bleeding	Dehydration, polycythemia
	F: 12–16 g/dL
Hematocrit	M: 42–52%	Fluid excess, anemia	Fluid deficit
	F: 36–48%
Platelets	150,000–400,000/mm³	Bleeding risk	Clotting risk

Electrolytes

Sodium (Na⁺)

Normal: 135–145 mEq/L
Low (Hyponatremia): < 135 — confusion, seizures, nausea
High (Hypernatremia): > 145 — agitation, thirst, dry mucous membranes

Potassium (K⁺)

Normal: 3.5–5.0 mEq/L
Low (Hypokalemia): < 3.5 — muscle weakness, arrhythmias, cramps
High (Hyperkalemia): > 5.0 — peaked T waves, cardiac arrest

Critical: K⁺ < 3.0 or > 6.0 requires immediate intervention

Calcium (Ca²⁺)

Normal: 8.5–10.5 mg/dL
Low (Hypocalcemia): tetany, Chvostek's sign, Trousseau's sign
High (Hypercalcemia): kidney stones, bone pain, "stones, bones, groans, moans"

Magnesium (Mg²⁺)

Normal: 1.5–2.5 mEq/L
Low: neuromuscular excitability, seizures
High: depressed reflexes, respiratory depression

Coagulation Studies

Test	Normal Range	What It Measures
PT	11–12.5 seconds	Extrinsic pathway (warfarin)
INR	0.8–1.2 (therapeutic 2–3)	Standardized PT
aPTT	30–40 seconds (therapeutic 1.5–2x)	Intrinsic pathway (heparin)
Bleeding time	1–9 minutes	Platelet function

Metabolic Panel

Glucose

Normal (fasting): 70–100 mg/dL
Hypoglycemia: < 70 — shakiness, diaphoresis, confusion
Hyperglycemia: > 100 — polyuria, polydipsia, polyphagia

BUN (Blood Urea Nitrogen)

Normal: 7–20 mg/dL
Elevated: kidney dysfunction, dehydration, high protein intake

Creatinine

Normal: 0.6–1.2 mg/dL
Elevated: kidney damage (more specific than BUN)

Liver Enzymes

ALT: 7–56 U/L
AST: 10–40 U/L
Bilirubin (total): 0.1–1.2 mg/dL
Albumin: 3.5–5.0 g/dL

Arterial Blood Gases (ABGs)

Parameter	Normal Range	Acidosis	Alkalosis
pH	7.35–7.45	< 7.35	> 7.45
PaCO₂	35–45 mmHg	> 45 (resp)	< 35 (resp)
HCO₃⁻	22–26 mEq/L	< 22 (meta)	> 26 (meta)
PaO₂	80–100 mmHg	< 80 hypoxia	—
SaO₂	95–100%	< 95%	—

ABG Analysis Steps

Look at pH → acidemia or alkalemia?
Look at PaCO₂ → respiratory cause? (moves in opposite direction)
Look at HCO₃⁻ → metabolic cause? (moves in same direction)
Determine compensation → is the other system trying to correct?

Cardiac Markers

Marker	Normal	Elevated Indicates
Troponin I	< 0.04 ng/mL	Myocardial infarction
CK-MB	< 5% of total CK	Heart muscle damage
BNP	< 100 pg/mL	Heart failure severity

Tips for Memorizing Lab Values

Group by system — learn electrolytes together, then cardiac markers, etc.
Use mnemonics:
- NaKCaMg for the main four electrolytes
- "135 to 145, sodium stays alive" for Na⁺ range
- "3.5 to 5, potassium keeps you alive" for K⁺ range
Practice daily — flashcards or app-based review
Learn critical values — know which abnormalities require immediate action

Nursing Implications to Remember

K⁺ out of range → check ECG, monitor for arrhythmias
Na⁺ changes → assess neurologic status (confusion, seizures)
Platelets < 50,000 → bleeding precautions (soft toothbrush, electric razor)
INR > 3 → bleeding risk, hold warfarin, notify provider
Glucose < 70 → give 15g fast-acting carbohydrate, recheck in 15 min

Master these lab values with practice questions in the ExamReady NCLEX app.

NCLEX Lab Values Cheat Sheet: Reference Ranges and Nursing Implications