A method for determining the risk of acute kidney injury (AKI) in a mammal following cardiac surgery is provided. The method comprises determining the sample value of IL-6 or hFABP concentration, or the ratio of IL-6 to IL-10, in a biological sample from the mammal, either prior to cardiac surgery or within 6 hours following surgery; comparing the sample value to a corresponding reference value; and determining that the mammal is at risk of acute kidney injury following cardiac surgery if the sample value is greater than the corresponding reference value.