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8.1 Laboratory Values: Hematology (CBC)

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NCLEX-RN Registered Nurse

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1 Introduction

About the NCLEX-RN Exam Next Generation NCLEX (NGN) Clinical Judgment Measurement Model (NCJMM) How to Use This Course

2 Chapter 2: Management of Care

2.1 Legal Rights and Responsibilities 2.2 Advance Directives and Self-Determination 2.3 Informed Consent Protocols 2.4 Client Advocacy and Rights (HIPAA) 2.5 Assignment, Delegation, and Supervision 2.6 Five Rights of Delegation 2.7 Scope of Practice (RN vs LPN vs UAP) 2.8 Ethical Practice Principles

3 Chapter 3: Safety and Infection Prevention and Control

3.1 Standard Precautions and Hand Hygiene 3.2 Transmission-Based Precautions (Contact, Droplet, Airborne) 3.3 PPE Donning and Doffing Sequences 3.4 Fall Prevention and Restraints 3.5 Fire Safety (RACE/PASS) 3.6 Disaster Triage and Emergency Response

4 Chapter 4: Health Promotion and Maintenance

4.1 Growth and Development (Erikson/Piaget) 4.2 Developmental Stages: Infancy through Older Adult 4.3 Maternal and Newborn Care (Antepartum) 4.4 Intrapartum Care and Fetal Monitoring 4.5 Postpartum Care (BUBBLE-HE) 4.6 Health Screening Guidelines 4.7 Immunization Schedules

5 Chapter 5: Psychosocial Integrity

5.1 Therapeutic Communication Techniques 5.2 Non-Therapeutic Communication (What to Avoid) 5.3 Anxiety Disorders and Mental Health Concepts 5.4 Schizophrenia: Hallucinations and Delusions 5.5 Depression and Suicide Assessment 5.6 Substance Misuse and Withdrawal 5.7 Grief and End-of-Life Care

6 Chapter 6: Basic Care and Comfort

6.1 Mobility and Hazards of Immobility 6.2 Assistive Devices (Crutches, Canes, Walkers) 6.3 Nutrition and Diet Therapy 6.4 Enteral Nutrition (Tube Feeding) 6.5 Bowel Elimination and Ostomy Care 6.6 Urinary Elimination and Catheter Care

7 Chapter 7: Pharmacological and Parenteral Therapies

7.1 Medication Administration Rights 7.2 Medication Calculations 7.3 High-Alert Medications: Insulins 7.4 High-Alert Medications: Anticoagulants 7.5 High-Alert Medications: Opioids 7.6 High-Alert Medications: Digoxin and Electrolytes 7.7 IV Therapy and Complications 7.8 Blood Product Administration 7.9 Total Parenteral Nutrition (TPN)

8 Chapter 8: Reduction of Risk Potential

8.1 Laboratory Values: Hematology (CBC) 8.2 Laboratory Values: Metabolic Panel (BMP) 8.3 Laboratory Values: Coagulation Studies 8.4 Vital Signs and Trend Recognition 8.5 Perioperative Care (Pre-Op and Post-Op) 8.6 Nasogastric Tubes and Therapeutic Procedures

9 Chapter 9: Physiological Adaptation

9.1 Fluid Imbalances (Hypovolemia and Hypervolemia) 9.2 Arterial Blood Gases (ABGs) and Acid-Base Balance 9.3 Medical Emergencies: Stroke (CVA) 9.4 Medical Emergencies: Myocardial Infarction (MONA) 9.5 Diabetic Emergencies (Hypoglycemia and DKA) 9.6 Respiratory Conditions (COPD, Pneumonia) 9.7 Cardiac Conditions (Heart Failure) 9.8 Neurological Conditions (Seizures)

8.1 Laboratory Values: Hematology (CBC)

Key Takeaways Explain This Topic AI

White Blood Cell (WBC) count normal range is 5,000-10,000/mm³; elevated WBC (leukocytosis) indicates infection, while low WBC (neutropenia) increases infection risk

Hemoglobin normal ranges are 12-16 g/dL for females and 14-18 g/dL for males; low hemoglobin indicates anemia and reduced oxygen-carrying capacity

Platelet count normal range is 150,000-400,000/mm³; thrombocytopenia (low platelets) significantly increases bleeding risk

Critical lab values require immediate notification to the provider and documentation of the time reported and provider response

The Complete Blood Count (CBC) is the most commonly ordered blood test and provides essential data about oxygen transport, immune function, and clotting ability

Last updated: January 2026

The Complete Blood Count (CBC) is the most frequently ordered laboratory test in clinical practice. It provides a snapshot of the blood's cellular components and is essential for assessing oxygen transport, immune function, and clotting ability. Mastering CBC interpretation is critical for the NCLEX-RN.

Why the CBC Matters

The CBC answers three fundamental questions about your patient:

  • Can they carry oxygen? (Red blood cells, hemoglobin)
  • Can they fight infection? (White blood cells)
  • Can they stop bleeding? (Platelets)
  • Red Blood Cell (RBC) Components
  • Hemoglobin (Hgb)

Hemoglobin is the protein in red blood cells that carries oxygen. It is the most clinically significant RBC value.

  • Parameter Normal Range Clinical Significance
  • Female 12-16 g/dL Oxygen-carrying capacity
  • Male 14-18 g/dL Higher due to testosterone

Low Hemoglobin (Anemia):

  • Causes: Blood loss, nutritional deficiencies (iron, B12, folate), chronic disease, bone marrow suppression
  • Signs/Symptoms: Fatigue, pallor, tachycardia, dyspnea on exertion
  • Nursing Action: Assess for bleeding, monitor vital signs, administer iron/B12 as ordered

High Hemoglobin (Polycythemia):

  • Causes: Dehydration (relative), chronic hypoxia (COPD), polycythemia vera
  • Risks: Increased blood viscosity, stroke risk
  • Nursing Action: Assess oxygenation status, encourage hydration
  • Hematocrit (Hct)

Hematocrit is the percentage of blood volume occupied by red blood cells.

  • Parameter Normal Range
  • Female 36-44%
  • Male 40-54%

Clinical Pearl: Hematocrit is approximately three times the hemoglobin value. If Hgb is 10 g/dL, expect Hct around 30%.

Red Blood Cell Count

  • Parameter Normal Range
  • Female 4.0-5.5 million/mm³
  • Male 4.5-6.0 million/mm³
  • White Blood Cell (WBC) Components

The WBC count reflects the body's immune status and ability to fight infection.

  • Parameter Normal Range Significance
  • Total WBC 5,000-10,000/mm³ Overall immune status
  • Leukocytosis (Elevated WBC > 10,000)

Common Causes:

  • Bacterial infection (most common)
  • Inflammation
  • Leukemia
  • Stress response
  • Corticosteroid therapy

Nursing Considerations:

  • Assess for signs of infection (fever, redness, drainage)
  • Monitor vital signs
  • Implement appropriate precautions
  • Leukopenia/Neutropenia (Low WBC < 5,000)

Common Causes:

  • Chemotherapy (bone marrow suppression)
  • Radiation therapy
  • Viral infections
  • Aplastic anemia

Nursing Considerations:

  • Implement neutropenic precautions
  • No fresh flowers or fruits (bacteria/fungi)
  • Strict hand hygiene
  • Avoid invasive procedures when possible
  • Monitor for signs of infection (may be subtle without WBC response)
  • WBC Differential

The differential tells you which type of white cells are elevated or decreased:

  • Cell Type Normal % Primary Function
  • Neutrophils 55-70% First responders to bacterial infection
  • Lymphocytes 20-40% Viral infections, immune memory
  • Monocytes 2-8% Phagocytosis, chronic infections
  • Eosinophils 1-4% Allergic reactions, parasitic infections
  • Basophils 0.5-1% Allergic and inflammatory responses

"Left Shift" - An increase in immature neutrophils (bands) indicates the bone marrow is releasing cells early to fight acute bacterial infection.

Platelets (Thrombocytes)

Platelets are essential for blood clotting and hemostasis.

  • Parameter Normal Range Critical Values
  • Platelet Count 150,000-400,000/mm³ < 50,000 (significant bleeding risk)
  • Thrombocytopenia (Low Platelets)

Common Causes:

  • Chemotherapy
  • Heparin-induced thrombocytopenia (HIT)
  • DIC (disseminated intravascular coagulation)
  • ITP (immune thrombocytopenic purpura)

Nursing Interventions:

  • Implement bleeding precautions
  • Use soft toothbrush
  • Electric razor only (no blade razors)
  • Avoid IM injections
  • Hold pressure on venipuncture sites for 5+ minutes
  • Monitor for petechiae, bruising, blood in stool/urine
  • Avoid NSAIDs and aspirin
  • Thrombocytosis (High Platelets > 400,000)
  • Risks: Increased clotting risk Nursing Action: Monitor for signs of DVT, PE, stroke
  • Critical Values Requiring Immediate Action
  • Test Critical Low Critical High
  • Hemoglobin < 7 g/dL > 20 g/dL
  • Hematocrit < 20% > 60%
  • WBC < 2,000/mm³ > 30,000/mm³
  • Platelets < 50,000/mm³ > 1,000,000/mm³

When you receive a critical value:

  • Verify the result (repeat if questionable)
  • Notify the provider immediately
  • Document the time notified and provider response
  • Intervene as ordered
  • On the Exam

Expect questions that present lab values and ask you to:

  • Identify which value is abnormal
  • Prioritize which patient to assess first
  • Select appropriate nursing interventions
  • Recognize when to notify the provider

Example Scenario: A patient receiving chemotherapy has a WBC of 1,800/mm³. The priority nursing action is to implement neutropenic precautions and protect the patient from infection.

  • Key Points for Practice
  • Memorize the normal ranges - they appear frequently
  • Low platelets = bleeding risk - think soft toothbrush, electric razor
  • Low WBC = infection risk - think hand hygiene, no fresh flowers
  • Low hemoglobin = anemia - think fatigue, tachycardia, pallor
  • Critical values = immediate notification - never delay reporting