BackgroundRefeeding syndrome (RFS) is a life‐threatening metabolic derangement occurring when nutrition is reintroduced after prolonged starvation. Limited data exist regarding RFS prevalence, risk factors, and outcome, particularly in critically ill patients.MethodsA retrospective cohort study was conducted in a medical intensive care unit from June 2018 to August 2020. RFS diagnostic criteria from the National Institute for Health and Care Excellence (NICE) and the American Society for Parenteral and Enteral Nutrition (ASPEN) were used. The primary outcome was 30‐day mortality.ResultsAmong 216 patients, RFS was diagnosed in 22.7% and 27.3% of patients per the NICE and ASPEN criteria, respectively. There was no significant difference in 30‐day mortality between patients with and without RFS (22/59 [37.3%] vs 53/157 [33.8%]; P = 0.627). Independent predictors of RFS were malignancy (odds ratio [OR] = 2.09; 95% CI = 1.06–4.15; P = 0.035), septic shock (OR = 2.26; 95% CI = 1.17–4.39; P = 0.016), and high NICE RFS risk classification (OR = 2.52; 95% CI = 1.20–5.31; P = 0.015). Factors associated with reduced RFS risk were Sequential Organ Failure Assessment (SOFA) scores >12 (OR = 0.45; 95% CI = 0.23–0.88; P = 0.020) and high‐dose vasopressor treatment (OR = 0.34; 95% CI = 0.14–0.79; P = 0.012).ConclusionRFS affected one‐fourth of the critically ill patients but did not significantly impact 30‐day mortality. Malignancy, septic shock, and high NICE RFS risk classification were positively associated with RFS, whereas high SOFA scores and extensive vasopressor use were linked to decreased risk.