What is the complete lab panel for evaluating fatigue and weakness?

Comprehensive Laboratory Panel for Evaluating Fatigue and Weakness

A comprehensive laboratory evaluation for fatigue and weakness should include complete blood count, comprehensive metabolic panel, thyroid function tests, inflammatory markers, iron studies, vitamin D level, and urinalysis as the core testing panel.

Initial Assessment and Quantification

• Use a numerical rating scale (0-10) to quantify fatigue severity:

  • 0-3: Mild fatigue
  • 4-6: Moderate fatigue
  • 7-10: Severe fatigue (associated with marked decrease in physical functioning) 1

• Distinguish between fatigue (subjective feeling of exhaustion) and weakness (objective reduction in muscle power) 2

Core Laboratory Panel

Basic Panels

1. Complete Blood Count (CBC) with differential

   • Evaluates for anemia, infection, and hematologic disorders 1

2. Comprehensive Metabolic Panel (CMP)

   • Includes electrolytes, glucose, kidney and liver function tests
   • Identifies metabolic disorders, organ dysfunction, and electrolyte imbalances 1

3. Thyroid Function Tests

   • TSH (primary screening test)
   • Free T4 (if TSH is abnormal)
   • Evaluates for hypothyroidism or hyperthyroidism 1, 3

Inflammatory and Nutritional Markers

1. Inflammatory Markers

   • Erythrocyte sedimentation rate (ESR)
   • C-reactive protein (CRP)
   • Screens for inflammatory conditions 1

2. Iron Studies

   • Serum iron
   • Ferritin
   • Total iron binding capacity (TIBC)
   • Transferrin saturation
   • Evaluates for iron deficiency and iron overload states 1

3. Vitamin D Level

   • 25-hydroxyvitamin D
   • Particularly important in patients with malabsorption conditions 1

4. Urinalysis

   • Screens for infection, kidney disease, and diabetes 1

Extended Testing Based on Clinical Suspicion

Endocrine Evaluation

• Fasting blood glucose/HbA1c (for diabetes)
• Cortisol levels (for adrenal insufficiency)
• Sex hormone levels (for hypogonadism) 4, 1

Cardiac Evaluation

• BNP or NT-proBNP (for heart failure)
• Additional electrolytes including calcium and magnesium 1

Autoimmune Evaluation

• Autoimmune markers if rheumatologic disease is suspected 1

Advanced Nutritional Assessment

• B12 and folate levels
• Full iron status including hepcidin level for persistent major fatigue 1

Important Considerations

• Normal laboratory values do not exclude fatigue-causing conditions; consider expanded testing when symptoms persist despite normal initial workup 1

• When fatigue is moderate to severe (≥4 on 0-10 scale), a more focused evaluation is warranted 4, 1

• Consider contributing factors beyond laboratory abnormalities:

  • Medication side effects (especially sedating medications)
  • Sleep disturbances
  • Emotional distress (depression and anxiety)
  • Pain
  • Activity level
  • Alcohol/substance use 4, 1

Special Populations

Cancer Patients

• Additional focus on disease status, treatment effects, and anemia 4
• Consider using validated fatigue assessment tools like Brief Fatigue Inventory (BFI) or FACIT-Fatigue 4

Inflammatory Bowel Disease

• Focus on nutritional deficiencies and inflammatory markers 4, 1
• Evaluate sleep quality and fatigue impact on quality of life 4

Remember that fatigue often clusters with sleep disturbance, emotional distress, and pain, requiring comprehensive assessment beyond laboratory testing 4. The laboratory evaluation should be tailored based on the clinical presentation and suspected underlying causes.