Nutritional deficiencies are common among morbidly obese patients. Data are scarce for patients who have undergone laparoscopic sleeve gastrectomy (LSG). The aim of the study is to clarify the prevalence of deficiencies and to identify risk factors for postoperative deficiencies. Hebrew University, Israel. Preoperative and 1-year postoperative data were collected. We included anthropometric parameters, obesity-related co-morbidities, and laboratory findings. There were 192 candidates. Seventy-seven of them completed follow-ups at 12 months. Before surgery, 15% had anemia. Deficiencies of iron, folate, and B12 were 47%, 32%, and 13%, respectively. Women were more deficient in iron (56% women, 26% men, P<.001). Before surgery, low levels of vitamin D and elevated parathyroid hormone (PTH) were 99% and 41%, respectively. One year postsurgery, the deficiencies of hemoglobin and vitamin B12 worsened (20% and 17%, P<.001, P = .048, respectively). One year postsurgery, deficiencies of iron, folate, vitamin D, and PTH improved (28%, 21%, 94%, and 10%, respectively). Deficiencies of hemoglobin, folate, and B12 before surgery were predictors for deficiencies 1 year after surgery (P = .006 OR = .090; P = .012 OR = .069; P = .062 OR = .165, respectively). LSG had a modest effect on nutritional deficiencies in our patients at 1-year postsurgery. Focusing on the preoperative nutritional status and tailoring a specific supplemental program for each individual should prevent postoperative deficiencies.