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), 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.
All Cards in This Deck
Question
What is the normal Hemoglobin (Hgb) range?
Answer
Males: 13.5–17.5 g/dL. Females: 12.0–15.5 g/dL. Low = anemia. High = polycythemia or dehydration.
Question
What is the normal Hematocrit (Hct) range?
Answer
Males: 41–53%. Females: 36–46%. Hct is approximately 3x the hemoglobin value. Low = anemia or bleeding.
Question
What is the normal Red Blood Cell (RBC) count?
Answer
Males: 4.5–5.5 million/µL. Females: 4.0–5.0 million/µL. Low = anemia. High = polycythemia.
Question
What is the normal White Blood Cell (WBC) count?
Answer
4,500–11,000 cells/µL (4.5–11 x10³/µL). Low (leukopenia) = infection risk. High (leukocytosis) = infection, inflammation, or leukemia.
Question
What is the normal Platelet count?
Answer
150,000–400,000/µL (150–400 x10³/µL). Low (thrombocytopenia) = bleeding risk. High (thrombocytosis) = clotting risk.
Question
What is the normal Sodium (Na+) level?
Answer
136–145 mEq/L. Low (hyponatremia) = confusion, seizures. High (hypernatremia) = thirst, dry mucous membranes, confusion.
Question
What is the normal Potassium (K+) level?
Answer
3.5–5.0 mEq/L. Low (hypokalemia) = muscle weakness, cardiac arrhythmias. High (hyperkalemia) = peaked T waves, cardiac arrest risk.
Question
What is the normal Calcium (Ca²+) level?
Answer
8.5–10.5 mg/dL. Low (hypocalcemia) = Trousseau's/Chvostek's signs, tetany. High (hypercalcemia) = "bones, stones, groans, psychic moans."
Question
What is the normal Magnesium (Mg²+) level?
Answer
1.5–2.5 mEq/L. Low (hypomagnesemia) = tremors, seizures, cardiac arrhythmias. High (hypermagnesemia) = respiratory depression, loss of deep tendon reflexes.
Question
What is the normal Phosphorus (PO4) level?
Answer
2.5–4.5 mg/dL. Has an inverse relationship with calcium — when Ca is high, phosphorus is low.
Question
What is the normal Blood Glucose level (fasting)?
Answer
70–100 mg/dL (fasting). 2-hour postprandial: < 140 mg/dL. Hypoglycemia < 70. Hyperglycemia > 126 (fasting, on two occasions = diabetes).
Question
What is the normal Blood Urea Nitrogen (BUN) level?
Answer
10–20 mg/dL. Elevated BUN indicates impaired kidney function, dehydration, or high protein intake.
Question
What is the normal Creatinine level?
Answer
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.
Question
What is the normal BUN:Creatinine ratio and what does it indicate?
Answer
Normal ratio: 10:1 to 20:1. Ratio > 20:1 suggests pre-renal causes (dehydration). Ratio < 10:1 suggests intrinsic renal disease.
Question
What is normal eGFR (estimated Glomerular Filtration Rate)?
Answer
> 60 mL/min/1.73m². eGFR < 60 for > 3 months indicates chronic kidney disease (CKD). < 15 = kidney failure.
Question
What is the normal Prothrombin Time (PT)?
Answer
11–13.5 seconds. Measures the extrinsic clotting pathway. Elevated in warfarin therapy, liver disease, Vitamin K deficiency.
Question
What is the normal INR and therapeutic range for warfarin?
Answer
Normal INR: 0.8–1.2. Therapeutic range for warfarin (most indications): 2.0–3.0. Mechanical heart valves: 2.5–3.5.
Question
What is the normal aPTT and therapeutic range for heparin?
Answer
Normal aPTT: 25–35 seconds. Therapeutic heparin range: 60–100 seconds (1.5–2.5 times normal).
Question
What is the normal pH of arterial blood (ABG)?
Answer
7.35–7.45. < 7.35 = acidosis. > 7.45 = alkalosis.
Question
What is the normal PaCO2 (ABG)?
Answer
35–45 mmHg. Controlled by the lungs (respiratory). High CO2 = respiratory acidosis. Low CO2 = respiratory alkalosis.
Question
What is the normal HCO3 (bicarbonate) (ABG)?
Answer
22–26 mEq/L. Controlled by the kidneys (metabolic). Low HCO3 = metabolic acidosis. High HCO3 = metabolic alkalosis.
Question
What is the normal PaO2 (ABG)?
Answer
80–100 mmHg. < 60 mmHg = respiratory failure. Used to assess oxygenation, not acid-base balance.
Question
What is the normal Oxygen Saturation (SpO2)?
Answer
95–100%. SpO2 < 90% is a medical emergency. Target for COPD patients: 88–92% (to avoid suppressing hypoxic drive).
Question
What are the normal Liver Function Tests (LFTs)?
Answer
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.
Question
What are the normal Thyroid Function Tests?
Answer
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.
Question
What is a critical potassium value that requires immediate action?
Answer
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.
Question
What is a critical glucose value requiring immediate action?
Answer
Blood glucose < 50 mg/dL (severe hypoglycemia) or > 500 mg/dL (DKA/HHS risk) requires immediate intervention.
Question
What is the normal Hemoglobin A1c (HbA1c)?
Answer
< 5.7% = normal. 5.7–6.4% = prediabetes. ≥ 6.5% = diabetes. Reflects average blood sugar over the past 2–3 months.
Question
What is the normal Serum Albumin level and clinical significance?
Answer
3.5–5.0 g/dL. Low albumin = malnutrition, liver disease, chronic illness. Also affects drug binding (many medications are albumin-bound).
Question
What are normal Troponin levels and their significance?
Answer
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.