Micronutrient deficiencies are highly prevalent in patients seeking metabolic-bariatric surgery (MBS), although literature remains scant in Asia. In this study, we assess the prevalence of nutritional deficiencies in patients with clinically severe obesity in Singapore and examine factors associated with the deficiencies.This is a prospective, observational study of 577 consecutive patients scheduled to undergo MBS. Nutritional profile including renal panel, calcium, phosphate, intact parathyroid hormone (iPTH), 25-hydroxyvitamin D (25(OH)D), vitamin B12, folate, ferritin, iron studies, hemoglobin, albumin, and alkaline phosphatase were analyzed.Mean age was 40.6 ± 10.3 years, 61.2% female, and mean BMI 42.4 ± 8.4 kg/m. 92.9% had suboptimal vitamin D levels; of which 25.6% had vitamin D insufficiency (25(OH)D < 30 mcg/L), 57.5% had vitamin D deficiency (25(OH)D < 20 mcg/L), and 9.8% had severe vitamin D deficiency (25(OH)D < 10 mcg/L). Younger age, female gender, and higher BMI were independent factors associated with lower 25(OH)D. There was an inverse relationship between iPTH and 25(OH)D, with an inflection point at 25(OH)D of approximately 20 mcg/L. Folate deficiency was present in 31% and vitamin B12 deficiency in 9.5% of the cohort. Serum ferritin levels were low in 29.3%. 25(OH)D, ferritin, serum iron, and albumin were also significantly higher in Chinese compared to Malay and Indian patients.2Vitamin D deficiency was the most common micronutrient deficiency observed in this multi-ethnic Asian cohort presenting for MBS. Ethnic differences in nutritional status were observed.