China: The RCR index is linked to higher mortality in diabetic nephropathy patients and can help assess severity and guide ICU treatment. Diabetic nephropathy, a severe complication of diabetes, significantly increases the risk of mortality, particularly among patients in intensive care units where metabolic disturbances are pronounced. The study included 1,265 critically ill DN patients, with a median age of 73 years and 64.27% being male. The findings highlight the prognostic significance of the RCR index in critically ill diabetic nephropathy patients. Association between red blood cell distribution width to serum calcium ratio and all-cause mortality in critically ill patients with diabetic nephropathy: a retrospective analysis of the MIMIC-IV database.