More than 60% of the adult US population now meets the criteria for being overweight or obese. Gastric bypass surgery has become a popular and effective way to combat this medical problem. Despite the success of these procedures, they are associated with many complications, including malnutrition, neurological compromise, and vitamin deficiency. Research has determined that even with multivitamin supplementation for life, a large percentage of bypass patients develop vitamin deficiencies. We present a case of beriberi after Roux-en-Y bypass that illustrates the importance of close follow up. A thorough review of vitamin deficiencies in this unique patient population is explored. Vitamin supplementation and treatment recommendations are compiled from the most up-to-date sources. Even patients on regular supplements should be closely monitored for vitamin deficiencies. Patient education regarding vitamin supplementation is vital; it should begin prior to surgery and continue throughout the postoperative period and beyond.