Key Takeaways
- 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
Laboratory Values: Hematology (CBC)
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
A nurse reviews laboratory results for a patient receiving chemotherapy. Which finding requires implementation of neutropenic precautions?
A patient has a platelet count of 45,000/mm³. Which nursing intervention is most important?
A patient's hemoglobin is 6.8 g/dL. What is the priority nursing action?