For a study, researchers sought to investigate the Red blood cell distribution width (RDW) as a diagnostic of sepsis prognosis. In total, 203 patients diagnosed with sepsis were brought into the intensive care unit. Analysis of the area under the receiver operating characteristic curve (AUC-ROC) of RDW dynamics, hospital mortality discrimination capacity, and the ability to provide value when paired with SOFA, LODS, SAPS-II, and APACHE-II scores. During the initial week following ICU admission, non-survivors had higher RDW values (P=0.048). When adjusting for Charlson, immunosuppression, nosocomial infection, NEWS2, SAPS-II, septic shock, and hemoglobin, only SOFA and RDW were independently related to death (P<0.05). After adjustment, the AUC-ROC for each model incorporating admission, 24, 48, 72-h, and 7-days RDW was 0.827, 0.822, 0.824, 0.834, and 0.812, respectively. 24-h RDW plus admission RDW increased the discrimination ability of the scores (SOFA AUC-ROC=0.772 vs 0.812 SOFA + admission RDW, P=0.041; LODS AUC-ROC = 0.687 vs 0.710, P=0.002; SAPS-II AUC-ROC = 0.734 vs 0.785, P=0.021; APACHE-II AUC-ROC = 0.672 vs 0.755, P=0.003). The admission RDW combined with the SOFA showed significantly improved mortality discrimination. The effectiveness of SOFA, LODS, APACHE-II, and SAPS in discriminating between patients with sepsis was improved by adding RDW as an independent prognostic marker of death. As a sign of systemic dysfunction and dysregulated inflammatory response, this metric might be included in prognosis evaluations and a useful tool.