CMSRN Lab Values Cheat Sheet
Print or save this quick-reference guide to standard adult lab values. Use it to memorize normal ranges and identify critical abnormalities on the test.
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Electrolytes (Basic Metabolic Panel)
Sodium (Na) — 135-145 mEq/L / Assess hydration and neurological status. Potassium (K) — 3.5-5.0 mEq/L / Critical for cardiac rhythm; monitor with diuretics. Calcium (Ca) — 8.5-10.5 mg/dL / Watch for tetany (low) or muscle weakness (high). Magnesium (Mg) — 1.5-2.5 mEq/L / Low levels trigger deep tendon reflex hyperactivity. Chloride (Cl) — 98-106 mEq/L / Shifts alongside sodium and acid-base imbalances. Phosphorus (PO4) — 2.5-4.5 mg/dL / Has an inverse relationship with calcium levels.
Hematology (Complete Blood Count)
White Blood Cells (WBC) — 5,000-10,000/mm3 / Elevated in infection; low in immunosuppression. Hemoglobin (Hgb) — Male: 14-18 g/dL, Female: 12-16 g/dL / Indicates oxygen-carrying capacity. Hematocrit (Hct) — Male: 42-52%, Female: 37-47% / Usually three times the hemoglobin value. Platelets (Plt) — 150,000-400,000/mm3 / Below 100,000 indicates thrombocytopenia and bleeding risk.
Renal Function & Urinalysis
Blood Urea Nitrogen (BUN) — 10-20 mg/dL / Elevated in dehydration or renal impairment. Creatinine — 0.6-1.2 mg/dL / The most specific indicator of kidney function. Urine Specific Gravity — 1.005-1.030 / High means concentrated urine; low means dilute.
Coagulation Studies
Prothrombin Time (PT) — 11-12.5 seconds / Used to monitor warfarin therapy. International Normalized Ratio (INR) — 0.8-1.1 (Normal) / Therapeutic for warfarin is typically 2.0-3.0. Partial Thromboplastin Time (aPTT) — 30-40 seconds / Used to monitor heparin; therapeutic is 1.5-2x normal.
Hepatic Function & Pancreas
Alanine Aminotransferase (ALT) — 4-36 units/L / Specific to liver damage. Aspartate Aminotransferase (AST) — 0-35 units/L / Rises with liver or muscle tissue damage. Total Bilirubin — 0.3-1.0 mg/dL / Elevated levels cause jaundice and indicate liver dysfunction. Amylase — 30-220 units/L / Rises rapidly in acute pancreatitis. Lipase — 0-160 units/L / More specific to pancreatic damage than amylase.
Cardiac & Inflammatory Markers
Troponin I — <0.03 ng/mL / Gold standard for detecting myocardial infarction. Brain Natriuretic Peptide (BNP) — <100 pg/mL / Elevated values indicate heart failure. C-Reactive Protein (CRP) — <1.0 mg/dL / General marker for systemic inflammation.
Arterial Blood Gases (ABGs)
pH — 7.35-7.45 / Determines overall acid-base status. PaCO2 — 35-45 mmHg / The respiratory component; inverse relationship with pH. HCO3 — 22-26 mEq/L / The metabolic component; direct relationship with pH. PaO2 — 80-100 mmHg / Measures oxygen dissolved in arterial blood.
Exam Facts to Remember
Passing Score — 95 / This is a standard scaled score, requiring about 71% correct. Scored Questions — 125 items / You must apply these lab values across five official domains. Largest Domain — Patient/Care Management / Makes up 32% (40 items) of the test. Recertification — Every 5 years / Requires 90 contact hours or re-examination. Practice — 5213 practice questions / Use our bank to test your clinical application of these values.
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