Abstract Abnormal phosphate concentrations are common in sepsis, but the prognostic relevance of serum phosphate and the association between recorded intravenous phosphate exposure and mortality remain uncertain. This retrospective cohort study used MIMIC-III, MIMIC-IV, and a single-center database from the First Affiliated Hospital of Chongqing Medical University. Adults with ICD-coded sepsis, a first ICU admission, and an ICU stay longer than 24 h were included.