Postoperative levels of fibroblast growth factor 23 (FGF23) are an early biomarker for predicting the development and severity of acute kidney injury (AKI), as well as short-term renal outcomes, according to a study of patients who underwent major surgery. FGF23 levels were significantly higher in patients who developed AKI compared to those without AKI. Higher FGF23 levels on the first postoperative day predicted worse AKI severity and need for renal replacement therapy, while levels on the third day best predicted short-term renal function outcomes. FGF23 appears to be a promising new biomarker for early AKI detection and prognosis.