Pediatric Lab Values Cheat Sheet for the CPN Exam
Memorize these standard pediatric lab ranges and how they differ from adult values to tackle the Assessment domain. Print or pin this guide for quick review during your study sessions.
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Complete Blood Count (CBC)
Hemoglobin (Newborn) — 14 to 24 g/dL / Much higher than adults due to fetal hemoglobin. Hemoglobin (Infant) — 10 to 15 g/dL / Drops as fetal RBCs break down (physiologic anemia). Hemoglobin (Child) — 11 to 16 g/dL / Gradually approaches adult levels. WBC Count (Newborn) — 9,000 to 30,000/mm3 / Elevated at birth is normal, drops rapidly. WBC Count (Child) — 5,000 to 10,000/mm3 / Mirrors standard adult ranges. Platelets — 150,000 to 400,000/mm3 / Consistent across pediatric and adult populations.
Basic Metabolic Panel (Electrolytes)
Sodium (Na) — 135 to 145 mEq/L / Same as adults; critical for hydration status. Potassium (K) (Infant) — 4.1 to 5.3 mEq/L / Slightly higher than adults; monitor closely with IV fluids. Potassium (K) (Child) — 3.4 to 4.7 mEq/L / Approaches adult norms; critical for cardiac function. Calcium (Total) — 8.8 to 10.8 mg/dL / Slightly higher in children due to active bone growth. Chloride (Cl) — 98 to 106 mEq/L / Mirrors adult ranges; shifts with sodium and acid-base balance.
Renal Function & Urinalysis
BUN (Infant/Child) — 5 to 18 mg/dL / Lower than adults due to smaller muscle mass and protein intake. Creatinine (Infant) — 0.2 to 0.4 mg/dL / Very low compared to adults; rises with muscle development. Creatinine (Child) — 0.3 to 0.7 mg/dL / Any value over 1.0 mg/dL in a young child requires urgent evaluation. Urine Specific Gravity — 1.005 to 1.030 / High indicates dehydration; infants cannot concentrate urine well. Urine Output (Infant) — 2 mL/kg/hr / Standard minimum for adequate hydration. Urine Output (Child) — 1 to 2 mL/kg/hr / Standard minimum; drops to 0.5 to 1 mL/kg/hr in adolescents.
Liver Function & Coagulation
Bilirubin (Total, Newborn) — 1 to 12 mg/dL / Peaks around day 3-5; levels >15 mg/dL often need phototherapy. Bilirubin (Total, Child) — 0.2 to 1.0 mg/dL / Matches adult levels once newborn jaundice resolves. AST/ALT — Varies by age / Generally higher in infants, settling to adult norms by late childhood. PT/PTT (Newborn) — Prolonged / Liver is immature; vitamin K given at birth prevents hemorrhagic disease.
Acid-Base Balance (ABGs)
pH (Child) — 7.35 to 7.45 / Same as adults; strict window for cellular function. PaCO2 (Child) — 35 to 45 mmHg / Respiratory component; infants decompensate quickly with respiratory distress. HCO3 (Infant/Child) — 20 to 28 mEq/L / Metabolic component; lower end is normal for infants compared to adults. PaO2 (Child) — 80 to 100 mmHg / Measured on room air; critical for assessing oxygenation.
CPN Exam Structure & Strategy
Assessment Domain — 35% of the exam (53 items) / Heavy focus on recognizing abnormal labs and baseline norms. Exam Format — 175 total questions (150 scored) / Fixed-form test, you have 180 minutes to finish. Pass Rate — Roughly 76-77% in 2022-2023 / Prepare thoroughly for all domains. Study Strategy — 2200+ practice questions / Drill these values in our bank to build rapid recognition.
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