Laboratory values are the language of the body — a window into a patient’s health status. For nurses, doctors, and medical students, knowing normal lab ranges and their clinical implications is critical for diagnosis, treatment, and safe medication administration.
This lab value cheat sheet provides a structured, easy-to-understand overview of the most important labs used in clinical practice:
- Vital Signs
- Basal Metabolic Panel (BMP)
- Renal Panel
- Liver Function Tests (LFTs)
- Pancreatic Enzymes
- Lipid Panel
- HbA1c (Diabetes marker)
- Complete Blood Count (CBC)
- Coagulation Values (PT, aPTT, INR)
- Arterial Blood Gases (ABGs)
- Other Critical Values (MAP, ICP, BMI, GCS)
Vital Signs – The First Lab Values
Although not laboratory tests, vital signs are the quickest indicators of patient stability.
- Blood Pressure: Normal = 120/80 mmHg
- Heart Rate: 60–100 BPM
- Respirations: 12–20 per minute
- Oxygen Saturation: 95–100%
- Temperature: 97.8°F – 99°F
Clinical Significance:
- Hypotension may indicate shock or sepsis.
- Tachycardia often signals fever, anemia, dehydration, or arrhythmias.
- Hypoxia (O2 < 90%) is critical and requires immediate intervention.
Basal Metabolic Panel (BMP)
The BMP evaluates electrolytes and kidney function.
- Sodium (Na⁺): 135–145 mEq/L
- Potassium (K⁺): 3.5–5.0 mEq/L
- Chloride (Cl⁻): 95–105 mEq/L
- Calcium (Ca²⁺): 9–11 mg/dL
- BUN (Blood Urea Nitrogen): 7–20 mg/dL
- Creatinine: 0.6–1.2 mg/dL
- Albumin: 3.4–5.4 g/dL
- Total Protein: 6.2–8.2 g/dL
Clinical Significance:
- Low sodium = hyponatremia → confusion, seizures.
- High potassium = hyperkalemia → life-threatening arrhythmias.
- Elevated BUN/creatinine = kidney dysfunction.
Renal Panel
Focused values for kidney health:
- Calcium: 9–11 mg/dL
- Magnesium: 1.5–2.5 mg/dL
- Phosphorus: 2.5–4.5 mg/dL
- Specific Gravity: 1.010–1.030 (urine concentration)
- GFR (Glomerular Filtration Rate): 90–120 mL/min/1.73m²
- Creatinine: 0.6–1.2 mg/dL
Nursing Note: GFR < 60 suggests chronic kidney disease.
Liver Function Tests (LFTs)
The liver is the body’s metabolic powerhouse.
- ALT (Alanine Aminotransferase): 7–56 U/L
- AST (Aspartate Aminotransferase): 5–40 U/L
- ALP (Alkaline Phosphatase): 40–120 U/L
- Bilirubin: 0.1–1.2 mg/dL
Clinical Significance:
- Elevated ALT/AST → hepatitis or liver injury.
- High bilirubin → jaundice, bile duct obstruction, or hemolysis.
Pancreatic Enzymes
- Amylase: 30–110 U/L
- Lipase: 0–150 U/L
Nursing Insight: Lipase is more specific for diagnosing acute pancreatitis.
Lipid Panel
Evaluates cardiovascular risk.
- Total Cholesterol: <200 mg/dL
- Triglycerides: <150 mg/dL
- LDL (Bad cholesterol): <100 mg/dL
- HDL (Good cholesterol): >60 mg/dL
Tip: High LDL increases atherosclerosis risk; high HDL protects against heart disease.
HbA1c – Diabetes Monitoring
- Normal: <5.6%
- Pre-diabetic: 5.7–6.4%
- Diabetic: >6.5%
Goal for Diabetics: <6.5% with good control.
Why it matters: HbA1c reflects average blood glucose over 3 months, not just daily fluctuations.
Complete Blood Count (CBC)
The CBC measures cellular components of blood.
- WBC (White Blood Cells): 4,500–11,000 /µL
- RBC (Red Blood Cells): 4.5–5.5 million /µL
- Platelets (PLT): 150,000–450,000 /µL
Hemoglobin (Hgb):
- Female: 12–16 g/dL
- Male: 13–18 g/dL
Hematocrit (Hct):
- Female: 36–48%
- Male: 39–54%
Clinical Relevance:
- Low Hgb/Hct = anemia.
- High WBC = infection or inflammation.
- Low platelets = bleeding risk.
Coagulation Studies (Coags)
Evaluate blood clotting.
PT (Prothrombin Time): 10–13 sec
PTT: 25–35 sec
aPTT: 30–40 sec (used with heparin therapy)
INR:
- Normal = 1
- On Warfarin = 2–3
Antidotes:
- Heparin → Protamine sulfate
- Warfarin → Vitamin K
Nursing Note: The higher the INR, the greater the bleeding risk.
Arterial Blood Gases (ABGs)
Measure acid–base balance and oxygenation.
- pH: 7.35–7.45
- PaCO₂: 35–45 mmHg
- PaO₂: 80–100 mmHg
- HCO₃⁻: 22–26 mEq/L
ROME Rule:
Respiratory Opposite, Metabolic Equal
- In respiratory disorders, pH and PaCO₂ move in opposite directions.
- In metabolic disorders, pH and HCO₃ move in the same direction.
Other Critical Values
MAP (Mean Arterial Pressure): 70–100 mmHg- Best = 15
- Mild = 13–15
- Moderate = 9–12
- Severe = 3–8
Quick Lab Value Reference Table
| Test | Normal Range |
|---|---|
| Sodium | 135–145 mEq/L |
| Potassium | 3.5–5.0 mEq/L |
| Creatinine | 0.6–1.2 mg/dL |
| Calcium | 9–11 mg/dL |
| WBC | 4,500–11,000 /µL |
| Hemoglobin (Male) | 13–18 g/dL |
| Hemoglobin (Female) | 12–16 g/dL |
| Platelets | 150,000–450,000 /µL |
| PT | 10–13 sec |
| INR on Warfarin | 2–3 |
| HbA1c (Diabetic) | >6.5% |
| pH (ABG) | 7.35–7.45 |
FAQs
Q1. Why do nurses memorize lab values?
Because prompt recognition of abnormal values allows quick intervention and prevents complications.
Q2. Which lab values are most critical to check before medication administration?
Potassium (before giving diuretics), INR (before anticoagulants), creatinine (before nephrotoxic drugs), and WBC count (before chemotherapy).
Q3. How often are labs checked in hospitalized patients?
Often daily for critical patients, but frequency depends on the condition and treatment plan.
Q4. Why is HbA1c preferred over fasting glucose?
Because it shows long-term glucose control, not just one point in time.
Q5. What is the first step when a lab value is abnormal?
Verify the result, assess the patient, and notify the provider immediately.
