What blood tests are required after bariatric surgery to monitor health and nutritional status?

Blood Test Monitoring After Bariatric Surgery

Regular blood tests are essential after bariatric surgery to monitor nutritional status, prevent deficiencies, and reduce morbidity and mortality associated with post-bariatric nutritional complications. 1

Core Blood Tests Required After Bariatric Surgery

First Year Monitoring Schedule

• 3,6, and 12 months post-surgery:
  • Full blood count and ferritin
  • Folate
  • Vitamin B12
  • Vitamin D (25-hydroxyvitamin D)
  • Calcium
  • Urea and electrolytes
  • Renal and liver function tests 1

Second Year Onwards

• Every 6 months in second year, then annually thereafter:
  • All tests listed above 1

Additional Tests Based on Surgery Type

For Malabsorptive Procedures (BPD/DS, OAGB/MGB with BP limb >150cm, SADIs)

• Additional monitoring required:
  • Vitamin A
  • Zinc
  • Copper
  • Selenium 1

For RYGB and Sleeve Gastrectomy

• Standard monitoring as outlined above is sufficient 1

Special Circumstances Requiring Additional Testing

Unexplained Anemia

• Check protein, zinc, copper, and selenium levels 1

Pregnancy After Bariatric Surgery

• Each trimester monitoring:
  • Ferritin
  • Folate
  • Vitamin B12
  • Calcium
  • Vitamin D
  • Vitamin A
  • Vitamins E and K (for patients with bypass or BPD/DS procedures) 1

Prolonged Vomiting/Poor Intake

• Check thiamine levels
• Immediate supplementation required (thiamine 200-300 mg daily) 1

Clinical Considerations and Pitfalls

Common Pitfalls

1. Inadequate pre-surgery correction of deficiencies

   • Pre-existing deficiencies are common in bariatric patients and should be corrected before surgery 2, 3

2. Loss to follow-up

   • Attrition rates for post-bariatric monitoring range from 3% to 63% 1
   • Implement digital communication methods to increase engagement

3. Vitamin B12 assessment limitations

   • Serum B12 levels are not always reliable indicators of deficiency
   • Consider methylmalonic acid testing if available when B12 deficiency is suspected despite normal levels 1

4. Masked deficiencies

   • Folic acid supplementation can mask vitamin B12 deficiency 1
   • Zinc and copper affect each other's absorption - maintain proper ratio (8-15mg zinc to 1mg copper) 1

Adolescent Patients

• Require more frequent nutritional assessment due to growth and development needs 1

Long-term Monitoring Recommendations

The evidence strongly supports lifelong monitoring of nutritional status. After the first two years with the bariatric surgery center, patients should continue annual nutritional monitoring as part of a shared care model with primary care providers 1, 4.

Patients with malabsorptive procedures should remain under specialist center care due to higher risk of nutritional deficiencies 1.

Importance of Compliance

Nutritional monitoring is not optional - it's essential for preventing serious complications including anemia, osteoporosis, and protein malnutrition that can significantly impact morbidity, mortality, and quality of life 3, 5. Studies show that many patients do not receive appropriate testing despite relatively high prevalence of deficiencies 6.