FGF23 levels significantly increase in female hip fracture patients who develop postoperative acute kidney injury (AKI). A pilot study measured FGF23 and creatinine levels in 9 female patients with postoperative AKI and 7 control patients without AKI. FGF23 levels were 39 times higher in the AKI group compared to controls, rising much more rapidly than creatinine. The findings suggest FGF23 may be a novel, early biomarker for detecting AKI after hip fracture surgery in women.