Preoperative and Postoperative Laboratory Testing for Gastric Bypass Surgery

Essential Preoperative Laboratory Tests

The American College of Gastroenterology recommends complete blood count (CBC) to evaluate for anemia and assess platelet count in patients undergoing gastric bypass surgery, with a prevalence of iron deficiency and anemia reported in 0-47% of patients preoperatively 1, 2
The Obesity Society suggests ferritin, folate, and vitamin B12 levels to screen for hematologic deficiencies, with folate deficiency ranging from 0-63% and vitamin B12 deficiency ranging from 0-23% preoperatively 1
The Endocrine Society recommends serum 25-hydroxyvitamin D levels to assess vitamin D status, with vitamin D deficiency reported in up to 99% of patients 1
The American College of Gastroenterology recommends coagulation studies including prothrombin time, partial thromboplastin time, and INR for patients undergoing percutaneous procedures 2
The National Institute of Diabetes and Digestive and Kidney Diseases suggests liver function tests to assess for non-alcoholic fatty liver disease (NAFLD) 3
The American Heart Association recommends lipid profile to assess cardiovascular risk 1, 3

The American College of Gastroenterology recommends regular monitoring of complete blood count, ferritin, folate, and vitamin B12 levels at regular intervals after gastric bypass surgery 3
The Endocrine Society suggests monitoring calcium, vitamin D, and PTH levels to monitor bone health 3
The National Institute of Diabetes and Digestive and Kidney Diseases recommends monitoring liver and kidney function tests after gastric bypass surgery 3
The American Diabetes Association suggests monitoring HbA1c for patients with preoperative diabetes 3

The Obesity Society reports that nutritional deficiencies are common in patients with obesity even before surgery, with vitamin D deficiency reported in up to 99% of patients 1
The American College of Gastroenterology notes that preoperative deficiencies should be corrected before surgery as patients have an increased risk of worsening deficiencies postoperatively 1

The American College of Gastroenterology warns against failing to check vitamin B12 levels when prescribing high-dose folic acid, as folic acid can mask B12 deficiency 3
The National Institute of Diabetes and Digestive and Kidney Diseases advises against overlooking the need for more frequent monitoring in patients with malabsorptive procedures 3
The Endocrine Society recommends checking zinc and copper simultaneously, as supplementation of one can affect levels of the other 3