What labs are recommended to evaluate for nutrition deficiency?

General Laboratory Tests for Nutritional Deficiency Evaluation

Routine electrolyte, mineral, and protein measurements are the recommended first-line laboratory tests to evaluate nutritional deficiencies, including hemoglobin, total lymphocyte count, albumin, prealbumin, and measurements of calcium, phosphorus, magnesium, and electrolytes. 1

Core Laboratory Panel for Nutritional Assessment

Essential Biochemical Markers:

• Proteins:

  • Albumin (reflects nutritional status from ~1 month prior)
  • Prealbumin/retinol-binding protein (reflects more recent nutritional status, ~1 week) 1
  • Total lymphocyte count 1
  • Hemoglobin 1

• Electrolytes and Minerals:

  • Sodium, potassium, chloride 1
  • Calcium, phosphorus, magnesium 1
  • Iron studies (serum iron, ferritin) 1
  • Triglycerides 1
  • Serum urea 1

• Vitamins:

  • Folate 1, 2
  • Vitamin B12 1, 2
  • Vitamin D 1

Additional Tests Based on Clinical Suspicion

For patients with specific risk factors or symptoms, consider adding:

• Extended Vitamin Panel:

  • Vitamin A 1
  • B vitamins (B1/thiamine, B6, riboflavin, niacin) 1
  • Vitamin C 1
  • Vitamin E 1

• Trace Elements:

  • Zinc 1
  • Selenium 1, 3
  • Copper 1
  • Chromium (for specific indications) 1

• Inflammatory Markers:

  • C-reactive protein (CRP) - essential to interpret other nutritional markers 4, 3
  • Erythrocyte sedimentation rate (ESR) 4

Special Considerations

Interpretation Challenges

• Always measure CRP simultaneously with nutritional markers as inflammation significantly affects the interpretation of most nutritional parameters 3
• Hypoalbuminemia in hospitalized patients is often due to inflammation rather than malnutrition 1
• Proteins with shorter half-lives (prealbumin, retinol-binding protein) better reflect recent nutritional changes than albumin 1

Patient-Specific Testing Frequency

• Long-term PN patients: Evaluate serum vitamin and trace element concentrations regularly 1
• Critically ill patients: May require daily monitoring 1
• Clinically stable patients: Measurements may be repeated 2-3 times per week 1
• Long-term nutritional supplementation: Laboratory monitoring every 6 months 1

High-Risk Populations

• Bariatric surgery candidates: High prevalence of deficiencies in vitamin D (80%), folate (32%), calcium (13.7%), and phosphorus (10.4%) 5
• Refeeding syndrome risk: Monitor phosphate, potassium, magnesium before and during feeding 1
• Vegetarians/vegans: Special attention to vitamin B12 status 2

Common Pitfalls to Avoid

1. Misinterpreting albumin levels - low albumin is often due to inflammation, not malnutrition 1, 4
2. Testing without measuring inflammation markers - CRP is essential for proper interpretation 3
3. Relying on a single marker - no single test is ideal for nutritional assessment 4
4. Ignoring clinical assessment - laboratory tests should complement, not replace, clinical evaluation 4
5. Testing at inappropriate times - some nutrients (like vitamin D) have seasonal variations 1
6. Overlooking medication effects - antibiotics, methotrexate, and other drugs can invalidate certain test results 2

Remember that laboratory assessment should be part of a comprehensive nutritional evaluation that includes anthropometric measurements and dietary intake assessment. The specific tests ordered should be guided by clinical suspicion and patient-specific risk factors.