Weight loss surgery creates specific and long-term vitamin and mineral supplementation requirements that differ fundamentally from general population recommendations. The reduced gastric capacity and, in malabsorptive procedures, shortened intestinal pathway create deficiency risks for iron, calcium, vitamin D, B12, and folate that standard dietary intake cannot adequately address. Understanding why these specific nutrients require supplementation — and why the supplement format matters — is foundational knowledge for any post-bariatric patient.