What initial bloodwork is recommended for patients presenting with fatigue?

Initial Bloodwork for Patients Presenting with Fatigue

The initial laboratory evaluation for patients presenting with fatigue should include complete blood count, comprehensive metabolic panel, thyroid-stimulating hormone, urinalysis, and inflammatory markers as the standard diagnostic workup. 1

Core Laboratory Tests

• Complete Blood Count (CBC) with differential

  • Evaluates for anemia, infection, and other hematologic abnormalities 1
  • Particularly important as minimum hemoglobin levels strongly correlate with fatigue severity 2

• Comprehensive Metabolic Panel (CMP)

  • Should include:
    • Electrolytes (including calcium and magnesium)
    • Blood urea nitrogen
    • Serum creatinine (renal function)
    • Liver function tests
    • Fasting blood glucose/glycohemoglobin 3, 1

• Thyroid-Stimulating Hormone (TSH)

  • Primary screening test for thyroid dysfunction 1
  • Consider free T4 if TSH is abnormal

• Urinalysis

  • Screens for infection, kidney disease, and diabetes 1

• Inflammatory Markers

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

• Lipid Profile

  • Should be included in the initial evaluation 3

Additional Tests Based on Clinical Suspicion

• Natriuretic peptides (BNP or NT-proBNP)

  • When heart failure is suspected 1
  • Particularly important in patients with dyspnea or exercise intolerance 3

• Iron Studies

  • Especially in patients with anemia or suspected iron deficiency
  • Iron deficiency with anemia significantly contributes to fatigue 3

• Vitamin D Levels

  • Particularly in patients with inflammatory bowel disease or other malabsorption conditions 3

Special Considerations

For patients with specific conditions or risk factors:

• Cardiac Evaluation

  • 12-lead electrocardiogram and chest radiograph (PA and lateral) for patients with suspected heart failure 3
  • Echocardiography if cardiac etiology is suspected

• Autoimmune Markers

  • Consider when rheumatologic disease is suspected 1

Fatigue Severity Assessment

Incorporate a standardized fatigue assessment:

• Visual Analog Scale (0-10) for fatigue severity 3
  • Scores 0-3: Mild fatigue requiring basic education and counseling
  • Scores 4-10: Moderate to severe fatigue requiring more thorough evaluation 3

Common Pitfalls to Avoid

1. Overlooking anemia: Minimum hemoglobin levels strongly correlate with fatigue severity, more so than mean hemoglobin 2

2. Focusing only on laboratory values: Remember to assess for sleep disturbances, emotional distress, pain, and medication side effects that contribute to fatigue 3

3. Missing subclinical disease: Normal laboratory values don't exclude fatigue-causing conditions; consider expanded testing when symptoms persist despite normal initial workup

4. Neglecting nutritional assessment: Deficiencies in vitamin D, magnesium, and other nutrients can contribute to fatigue, particularly in patients with malabsorption 3

By following this systematic approach to laboratory evaluation, clinicians can efficiently identify the underlying causes of fatigue and develop appropriate treatment strategies.