Prevalence and Associations of Preoperative Micronutrient Deficiencies in Bariatric Surgery Candidates with Severe Obesity

Aim: To determine the prevalence of preoperative micronutrient deficiencies in bariatric surgery candidates with severe obesity and to examine associations with BMI, age, and sex. Methods: This single-center retrospective observational study included 411 adults (BMI ≥ 35 kg/m 2 ) evaluated for bariatric surgery (2016– 2021). Routine chemistry and hematology tests were performed using automated analyzers, hormones and vitamins were measured using automated immunoassays, and trace elements were quantified using validated spectrometric laboratory methods. Deficiency thresholds were based on institutional reference limits and bariatric nutrition guidance. Results: The most frequent deficiencies were severe vitamin D deficiency (25[OH]D < 10 ng/mL; 42.4%) and selenium deficiency (34.1%). Patients with BMI ≥ 50 kg/m 2 had higher potassium and PTH levels (p< 0.05). With increasing age, sodium, urine calcium, and folate levels increased, whereas albumin decreased (p< 0.05). Male patients had higher levels of several micronutrients (including vitamin B12, vitamin D, and zinc) compared with females (p< 0.05). Age and sex distributions did not differ significantly across BMI groups. Conclusion: Preoperative micronutrient deficiencies are common in bariatric surgery candidates, particularly severe vitamin D and selenium deficiency. These findings support guideline-based preoperative screening and targeted correction of deficiencies to optimize perioperative nutritional status.