Bariatric surgeons and dietitians universally emphasize the critical importance of scheduled blood work to track ferritin, zinc, B12, folate, vitamin D, and comprehensive metabolic panels. Testing should occur pre-operatively to establish baseline values, then at 3, 6, and 12 months post-surgery, and annually thereafter for life. Many programs recommend even more frequent monitoring for high-risk patients or those experiencing significant hair loss. These tests identify deficiencies before they become symptomatic, allowing for early intervention and dose adjustment of supplements.