Sepsis-associated acute kidney injury (SA-AKI) substantially worsens clinical outcomes, yet reliable prognostic biomarkers remain limited. Dysregulation of lipid metabolism, particularly elevated triglycerides (TG) and decreased high-density lipoprotein cholesterol (HDL-C), may mirror the severity of critical illness. In this retrospective cohort study based on the Medical Information Mart for Intensive Care IV database, we investigated whether a logarithmic lipid ratio, log(TG_max/HDL_min), obtained during the first week of intensive care, predicts adverse outcomes among 1633 adults with SA-AKI. Higher log(TG_max/HDL_min) was independently associated with increased 1-year mortality and prolonged lengths of stay in both the intensive care unit and hospital after multivariable adjustment for age, sex, blood urea nitrogen, serum creatinine, and Sequential Organ Failure Assessment (SOFA) score. These associations were particularly pronounced in non-diabetic and insulin-naïve individuals. Restricted cubic spline analyses demonstrated a J-shaped relationship between the lipid ratio and mortality risk, and the model showed acceptable discrimination (area under the curve 0.816). These findings suggest that early elevation of log(TG_max/HDL_min) serves as a simple and accessible indicator of metabolic dysfunction and a potential risk marker associated with adverse outcomes in patients with SA-AKI. Further prospective studies are needed to confirm these associations and to explore potential clinical implications.