What are the typical lab value ranges in a Comprehensive Metabolic Panel (CMP)?

Normal Lab Value Ranges in a Comprehensive Metabolic Panel (CMP)

A Comprehensive Metabolic Panel (CMP) includes 14 standard tests that evaluate organ function, electrolyte balance, and glucose metabolism with specific reference ranges for each component.

Electrolytes

• Sodium: 135-145 mEq/L (135-145 mmol/L)
• Potassium: 3.5-5.0 mEq/L (3.5-5.0 mmol/L)
• Chloride: 98-107 mEq/L (98-107 mmol/L)
• Carbon Dioxide (CO2): 22-30 mEq/L (22-30 mmol/L)

Kidney Function

• Blood Urea Nitrogen (BUN): 7-20 mg/dL (2.5-7.1 mmol/L)
• Creatinine: 0.6-1.2 mg/dL (53-106 μmol/L) for males; 0.5-1.1 mg/dL (44-97 μmol/L) for females

Glucose Metabolism

• Glucose (fasting): 70-99 mg/dL (3.9-5.5 mmol/L)
  • Prediabetes: 100-125 mg/dL (5.6-6.9 mmol/L) 1
  • Diabetes: ≥126 mg/dL (≥7.0 mmol/L) 1

Liver Function Tests

• Albumin: 3.5-5.0 g/dL (35-50 g/L)
• Total Protein: 6.0-8.3 g/dL (60-83 g/L)
• Alkaline Phosphatase (ALP): 40-129 U/L
• Alanine Aminotransferase (ALT): 7-56 U/L
• Aspartate Aminotransferase (AST): 10-40 U/L
• Total Bilirubin: 0.1-1.2 mg/dL (1.7-20.5 μmol/L)

Calcium Balance

• Calcium: 8.5-10.5 mg/dL (2.1-2.6 mmol/L)

Important Considerations

Diagnostic Implications

• Glucose values can be used for diabetes diagnosis with specific cutoffs:
  • Fasting glucose ≥126 mg/dL (7.0 mmol/L) 1
  • Random glucose ≥200 mg/dL (11.1 mmol/L) with symptoms 1
  • However, portable glucose meters should not be used for diabetes diagnosis 1

Variations in Reference Ranges

• Reference ranges may vary slightly between laboratories
• Age, sex, and pregnancy can affect normal ranges
• Values should be interpreted in clinical context

Common Pitfalls in Interpretation

1. Dehydration: Can falsely elevate BUN, creatinine, and protein levels
2. Hemolysis: Can falsely elevate potassium and some liver enzymes
3. Medications: Many drugs can affect liver function tests and other parameters
4. Fasting status: Non-fasting samples can elevate glucose and triglycerides
5. Timing: Some values (like glucose) have diurnal variations

Clinical Applications

• CMPs are commonly used for:
  • Routine health screenings
  • Monitoring chronic diseases
  • Medication management
  • Preoperative evaluation
  • Diagnosis of various conditions

Special Considerations

• For patients with diabetes, target glucose ranges are:
  • Fasting: 80-130 mg/dL (4.4-7.2 mmol/L) 1
  • Post-prandial: <180 mg/dL (<10.0 mmol/L) 1
• For pregnant women with gestational diabetes, target glucose values are:
  • Fasting: <95 mg/dL (<5.3 mmol/L) 1
  • 1-hour postprandial: <140 mg/dL (<7.8 mmol/L) 1
  • 2-hour postprandial: <120 mg/dL (<6.7 mmol/L) 1

Point-of-care CMP testing has been shown to reduce emergency department length of stay by approximately 22 minutes compared to central laboratory testing 2, but should not be used for diagnostic purposes.