Acute kidney injury (AKI) is primarily defined and staged according to the magnitude of the rise in serum creatinine. Here we sought to determine if the duration of AKI adds additional prognostic information above that from the magnitude of injury alone. We prospectively studied 35,302 diabetic patients from 123 Veterans Affairs Medical Centers undergoing their first noncardiac surgery. The main outcome was long-term mortality in those who survived the index hospitalization. AKI was stratified by magnitude according to AKI Network stages and by the duration (short (less than 2 days), medium (3-6 days) or long (7 days or more)). Overall, 17.8% of patients experienced at least stage 1 AKI or greater following surgery. Both the magnitude and duration of AKI were significantly associated with long-term survival in a dose-dependent manner. Within each stage, longer duration of AKI was significantly associated with a graded higher rate of mortality. However, within each of the duration categories, the stage was not associated with mortality. When considered separately in multivariate analyses, both a higher stage and duration were independently associated with increased risk of long-term mortality. Hence, the duration of AKI adds additional information to predict long-term mortality.