From the Guidelines
Regular lab monitoring is essential after gastric bypass surgery to prevent and detect nutritional deficiencies and metabolic complications, with a recommended monitoring schedule of 3,6, and 12 months post-surgery, then annually thereafter. This monitoring schedule is crucial because gastric bypass alters the digestive anatomy, reducing nutrient absorption capacity, particularly for iron, calcium, and fat-soluble vitamins 1. Key tests should include:
- Complete blood count to monitor for anemia
- Comprehensive metabolic panel to assess kidney and liver function
- Lipid panel
- HbA1c for diabetes monitoring
- Vitamin levels including B12, folate, iron studies, vitamin D, calcium, and parathyroid hormone Additional monitoring should include zinc, copper, selenium, and vitamins A, E, and K in patients with malabsorptive procedures, as suggested by the British Obesity and Metabolic Surgery Society guidelines 1. Thiamine levels should be checked if neurological symptoms develop. The most recent guidelines from 2022 suggest assessing the nutritional status of patients undergoing bariatric procedures, including Vitamin D, folic acid, B12, B6, and B1 serum level, due to the high risk of vitamin B complex deficiency and malnutrition 1. Laboratory results should guide personalized supplement regimens, which typically include a high-quality multivitamin, calcium citrate with vitamin D, iron, and vitamin B12. Patients with pre-existing deficiencies or those who struggle with supplement adherence may require more frequent monitoring.
From the Research
Lab Monitoring After Gastric Bypass Surgeries
- Gastric bypass surgery is associated with many complications, including malnutrition, neurological compromise, and vitamin deficiency 2.
- Long-term laboratory monitoring is recommended after gastric bypass surgery to prevent the development of micronutrient deficiencies 3.
- The risk of nutritional deficiencies depends on the percentage of weight loss and the type of surgical procedure performed, with iron deficiency being common in menstruating women and Roux-en-Y gastric bypass (GBP) being associated with an increased risk of calcium, vitamin D, and vitamin B12 deficiencies 4.
- Nutrient deficiencies after gastric bypass surgery are common and have multiple causes, including preoperative factors such as obesity and preoperative weight loss, and postoperative factors such as reduced food intake, suboptimal dietary quality, altered digestion and absorption, and nonadherence with supplementation regimens 5.
- Long-term follow-up with blood tests is essential for bariatric surgery to be a successful treatment for obesity and related co-morbidities, with many patients having better vitamin levels after the operation, but also an increase of parathyroid-hormone and ongoing iron depletion up to 5 years post surgery 6.
Recommended Lab Tests
- Tests recommended by an expert panel on bariatric surgery, including tests recommended routinely as well as second-line tests for specific clinical scenarios, such as tests for anemia when iron deficiency is not present 3.
- Routine nutritional screening, recommendations for appropriate supplements, and monitoring compliance are imperative, whatever the bariatric procedure 4.
- Blood tests, including tests for ferritin, mean-corpuscular-volume, thrombocytes, vitamin D, parathyroid-hormone, glycated hemoglobin (HbA1C), triglyceride, total-cholesterol, C-reactive-protein, gamma-glutamyl-transferase, alkaline-phosphatase, creatinine, vitamin B1, and total protein, should be performed regularly to monitor for nutrient deficiencies and other complications 6.
Frequency of Lab Testing
- Most gastric bypass patients do not undergo routine laboratory testing in the first year after their surgery, ranging from 54% (electrolytes) to 95% (zinc) 3.
- Patients undergoing gastric bypass do not routinely undergo recommended laboratory tests, although they are undergoing more monitoring than gastric banding patients 3.
- Five-year follow-up was 58% in one study, highlighting the need for long-term follow-up, including blood tests 6.