Background and aims: Acute kidney injury (AKI) is a common clinical syndrome that has been consistently linked with increased morbidity and mortality risk. Prognosis, as well as incidence, varies depending on patients characteristics and health care setting. We aimed to evaluate the incidence of AKI and related outcomes in a population of hospitalised patients taking into account the time of onset and severity of the syndrome. Methods: This retrospective study included adult patients admitted to a tertiary care hospital between January 1, 2013, and December 31, 2015, who had at least one inpatient serum creatinine (SCr). We distinguished between AKI apparent at admission (CA-) and afterwards during hospitalisation (HA-AKI). Results: The incidence of AKI was 15.2 %, of which 68% of episodes developed during hospital care. Baseline characteristics of CA-AKI and HA-AKI were similar, but CA-AKI patients were more likely to have more severe episodes and shorter length of stay than patients with HA-AKI (30.9% vs 14.5% with AKI stage 3 and 8.1 vs 14.8 days, respectively). We found a strong, gradual association (after multivariate adjustment) between stage of AKI and mortality. Irrespective the type of AKI, stage 3 was related to the five-fold risk of in-hospital death and a two-fold risk of death at the 6th-month in comparison to No AKI. Conclusions: One in six of hospitalised patients experienced AKI, and almost two-thirds of events developed during the hospital stay. There were no differences in short-term mortality between AKI type, but the risk of death related to the severity of the syndrome.