From the Guidelines
Patients with a history of gastric bypass surgery should have regular laboratory monitoring including complete blood count (CBC), comprehensive metabolic panel (CMP), vitamin B12, folate, iron studies (ferritin, iron, TIBC), vitamin D, calcium, parathyroid hormone (PTH), zinc, copper, and vitamin A levels, with monitoring frequency guided by the most recent guidelines. The most recent guidelines from the British Obesity and Metabolic Surgery Society, published in 2020 1, recommend checking full blood count and serum ferritin at regular intervals post-surgery, with consideration of monitoring frequency at 3,6, and 12 months in the first year and at least annually thereafter. Key laboratory tests to order include:
- Complete blood count (CBC) to monitor for anemia and other hematological abnormalities
- Comprehensive metabolic panel (CMP) to assess electrolyte and renal function
- Vitamin B12 and folate levels to monitor for deficiencies due to altered absorption
- Iron studies (ferritin, iron, TIBC) to assess iron deficiency anemia
- Vitamin D, calcium, and parathyroid hormone (PTH) levels to monitor for bone density issues
- Zinc, copper, and vitamin A levels to assess for other potential deficiencies These tests should be performed at least annually, with more frequent monitoring in the first year post-surgery, as recommended by the guidelines 1. Additionally, hemoglobin A1C should be checked in patients with pre-existing diabetes, as recommended by general clinical practice. The importance of regular monitoring is highlighted by the potential for deficiencies to occur even with normal serum concentrations, as noted in the study on vitamin B12 absorption post-bariatric surgery 1. Regular monitoring allows for early detection of deficiencies and appropriate supplementation before clinical symptoms develop, ultimately improving morbidity, mortality, and quality of life outcomes for patients with a history of gastric bypass surgery.
From the Research
Laboratory Tests for Patients with a History of Gastric Bypass Surgery
Patients who have undergone gastric bypass surgery are at risk of developing micronutrient deficiencies, including anemia, iron deficiency, vitamin B12 deficiency, and vitamin D deficiency 2, 3, 4. The following laboratory tests are recommended to monitor these patients:
- Complete blood count (CBC) to check for anemia 2, 4
- Iron studies, including serum iron, total iron-binding capacity (TIBC), and ferritin 2, 4
- Vitamin B12 levels 2, 4, 5
- Vitamin D levels 4, 6
- Electrolyte panel, including magnesium and zinc 3, 6
- Folate levels 2, 4
- Liver function tests (LFTs) and renal function tests to monitor for any potential complications 3
Frequency of Laboratory Testing
The frequency of laboratory testing for patients with a history of gastric bypass surgery is crucial to prevent the development of micronutrient deficiencies. Studies have shown that most patients do not undergo routine laboratory testing in the first year after surgery, ranging from 54% to 95% 3. It is recommended that patients undergo laboratory testing at least annually, with more frequent testing in the first year after surgery 3, 4.
Nutritional Deficiencies and Supplementation
Patients with a history of gastric bypass surgery are at risk of developing nutritional deficiencies, including vitamin B12, iron, and vitamin D deficiencies 2, 4, 5, 6. Supplementation with multivitamins, iron, and vitamin B12 is often necessary to prevent these deficiencies 2, 5, 6. The appropriate oral dose of crystalline vitamin B12 to correct low serum vitamin B12 levels is at least 350 µg per day 5.