Deficiencies in vitamins and other nutrients are common following the Roux-en-Y gastric bypass (RYGBP), biliopancreatic diversion (BPD) and biliopancreatic diversion with duodenal switch (BPDDS), and may become clinically significant if not recognized and treated with supplementation. This paper presents a review of the current literature and evidence of the most commonly deficient vitamins and minerals following weight loss surgery, including protein, iron, vitamin B₁₂, folate, calcium, the fat-soluble vitamins (A, D, E, K), and other micronutrients. The deficiencies appear to be more substantial following malabsorptive procedures such as BPD, but occur with restrictive procedures as well. The review suggests that further studies are needed to evaluate the clinical significance of the nutritional deficiencies, and to determine guidelines for supplementation.