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Nursing Lab Values Reference

Knowing normal laboratory reference ranges is a fundamental nursing skill tested on the NCLEX and required in every clinical setting. This flashcard deck covers the most important lab values across all body systems, including complete blood count (CBC),...

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Knowing normal laboratory reference ranges is a fundamental nursing skill tested on the NCLEX and required in every clinical setting. This flashcard deck covers the most important lab values across all body systems, including complete blood count (CBC), basic metabolic panel (BMP), coagulation studies, liver function tests, thyroid function, arterial blood gases (ABGs), and critical "panic" values that require immediate nursing action. Each card presents the lab test name, normal reference range, clinical significance, and what abnormal values may indicate. Based on standard nursing textbook reference ranges and NCSBN NCLEX-RN guidelines.

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Males: 13.5–17.5 g/dL. Females: 12.0–15.5 g/dL. Low = anemia. High = polycythemia or dehydration.
Males: 41–53%. Females: 36–46%. Hct is approximately 3x the hemoglobin value. Low = anemia or bleeding.
Males: 4.5–5.5 million/µL. Females: 4.0–5.0 million/µL. Low = anemia. High = polycythemia.
4,500–11,000 cells/µL (4.5–11 x10³/µL). Low (leukopenia) = infection risk. High (leukocytosis) = infection, inflammation, or leukemia.
150,000–400,000/µL (150–400 x10³/µL). Low (thrombocytopenia) = bleeding risk. High (thrombocytosis) = clotting risk.
136–145 mEq/L. Low (hyponatremia) = confusion, seizures. High (hypernatremia) = thirst, dry mucous membranes, confusion.
3.5–5.0 mEq/L. Low (hypokalemia) = muscle weakness, cardiac arrhythmias. High (hyperkalemia) = peaked T waves, cardiac arrest risk.
8.5–10.5 mg/dL. Low (hypocalcemia) = Trousseau's/Chvostek's signs, tetany. High (hypercalcemia) = "bones, stones, groans, psychic moans."
1.5–2.5 mEq/L. Low (hypomagnesemia) = tremors, seizures, cardiac arrhythmias. High (hypermagnesemia) = respiratory depression, loss of deep tendon reflexes.
2.5–4.5 mg/dL. Has an inverse relationship with calcium — when Ca is high, phosphorus is low.
70–100 mg/dL (fasting). 2-hour postprandial: < 140 mg/dL. Hypoglycemia < 70. Hyperglycemia > 126 (fasting, on two occasions = diabetes).
10–20 mg/dL. Elevated BUN indicates impaired kidney function, dehydration, or high protein intake.
Males: 0.7–1.3 mg/dL. Females: 0.6–1.1 mg/dL. Elevated creatinine = impaired kidney function. More specific for renal disease than BUN.
Normal ratio: 10:1 to 20:1. Ratio > 20:1 suggests pre-renal causes (dehydration). Ratio < 10:1 suggests intrinsic renal disease.
> 60 mL/min/1.73m². eGFR < 60 for > 3 months indicates chronic kidney disease (CKD). < 15 = kidney failure.
11–13.5 seconds. Measures the extrinsic clotting pathway. Elevated in warfarin therapy, liver disease, Vitamin K deficiency.
Normal INR: 0.8–1.2. Therapeutic range for warfarin (most indications): 2.0–3.0. Mechanical heart valves: 2.5–3.5.
Normal aPTT: 25–35 seconds. Therapeutic heparin range: 60–100 seconds (1.5–2.5 times normal).
7.35–7.45. < 7.35 = acidosis. > 7.45 = alkalosis.
35–45 mmHg. Controlled by the lungs (respiratory). High CO2 = respiratory acidosis. Low CO2 = respiratory alkalosis.
22–26 mEq/L. Controlled by the kidneys (metabolic). Low HCO3 = metabolic acidosis. High HCO3 = metabolic alkalosis.
80–100 mmHg. < 60 mmHg = respiratory failure. Used to assess oxygenation, not acid-base balance.
95–100%. SpO2 < 90% is a medical emergency. Target for COPD patients: 88–92% (to avoid suppressing hypoxic drive).
ALT: 7–56 U/L. AST: 10–40 U/L. Alkaline Phosphatase: 44–147 U/L. Total Bilirubin: 0.2–1.2 mg/dL. Elevated = liver disease or damage.
TSH: 0.4–4.0 mIU/L (most sensitive test). Free T4: 0.8–1.8 ng/dL. High TSH + Low T4 = hypothyroidism. Low TSH + High T4 = hyperthyroidism.
K+ < 2.5 mEq/L or > 6.0 mEq/L are critical values requiring immediate notification of the provider due to life-threatening cardiac arrhythmia risk.
Blood glucose < 50 mg/dL (severe hypoglycemia) or > 500 mg/dL (DKA/HHS risk) requires immediate intervention.
< 5.7% = normal. 5.7–6.4% = prediabetes. ≥ 6.5% = diabetes. Reflects average blood sugar over the past 2–3 months.
3.5–5.0 g/dL. Low albumin = malnutrition, liver disease, chronic illness. Also affects drug binding (many medications are albumin-bound).
Troponin I: < 0.04 ng/mL. Troponin T: < 0.01 ng/mL. Elevated troponin = myocardial infarction (heart attack). The gold standard cardiac biomarker. Rises within 3–4 hours of MI.