The "MUST KNOW" Labs for the NCLEX
It is common to see “normal lab values” that differ slightly from what you see in your textbook or at the hospital. Laboratory reference values often vary among reference sources and are highly dependent on the analytic methods used.
The NCLEX will not ask you to identify lab values with only slight variations from the norm because of this widely-known fact! Instead, questions on lab values will be obviously “off” or else you will be told about an abnormal lab result and then tested on your understanding of the implications of that result: can you anticipate the manifestations, the risks associated with it, or how to intervene?
Don’t focus on memorizing every reference range, but do learn the ones that are likely to show up on the NCLEX. The following labs are specifically listed on the detailed version of the NCLEX Test Blueprint:
• HCO3: 21 - 28 mEq/L or 21 - 28 mmol/L
• BUN: 10-20 mg/dL or 3.6-7.1 mmol/L
• Creatinine 0.5-1.2 mg/dL or 44-106 µmol/L.
• Cholesterol (total): <200 mg/dL or <5.0 mmol/L
• Glucose: 70 - 110 mg/dL (fasting) and ≥ 200 (casual) or <6.1 mmol/L (fasting) or ≥ 11.1 mmol/L (casual).
• Critical glucose levels are <40 and >400 mg/dL or <2.22 and >22.2 mmol/L .
• Hematocrit: 37-52% or 0.37-0.52 volume fraction
• Hemoglobin: 12-18 g/dL or 120-180 mmol/L
• HbA1C: 4-5.9% (nondiabetic), < 7% (good diabetic control), > 9% (poor diabetic control)
• Platelets: 150,000-400,000/mm³ or 150-400 x10⁹/L.
• Potassium: 3.5-5.0 mEq/L or 3.5-5 mmol/L.
• Sodium: 136-145 mEq/L or 136/145 mmol/L.
• WBC: 5,000-10,000/mm³ or 5-10 x10⁹/L.
• Critical WBC: <2,000 or >40,000/mm³ or <2 or >40x10⁹/L.
• PT: 11-12.5 seconds (normal) or ≥1.5-2 x control (with anticoagulant therapy)
• aPTT: 30-40 seconds (normal) or ≥1.5-2.5 x control (with anticoagulant therapy)
• INR: 0.8 - 1.1 (normal) or 2 - 3 (for A - fib) or 3 - 4.5 (for prosthetic valves)
NCLEX Mastery provides lab reference ranges from Mosby’s, 5th Edition (2013) and Mosby’s Canadian (2012). In a few instances, SI ranges have been sourced from Stedman’s Online or conversions made from Mosby’s conventional values, calculated using the AMA Manual of Style SI Conversion Calculator.
For a complete lab resource, broken down by gender and age group, consult any of our nursing apps.
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