Urea and creatinine have been key indicators of kidney function for years and can be measured easily and quickly with currently available whole blood point of care analyzers. While newer tests for assessing renal function may hold promise for the future, they currently lack the history and clinical familiarity of urea, creatinine, and their ratio. In addition, the urea:creatinine ratio still has significant value in selected patient populations, particularly critically ill patients, COVID-19 patients, and trauma patients. This webinar will describe the biochemisty of urea and creatinine production, and the physiology and handling of these metabolites by the kidneys as a lead-in to a discussion of the urea:creatinine ratio. New clinical studies will be summarized that describe the utility of the urea:creatinine ratio as a rapid, easy to obtain parameter to gauge the severity of the illness and the likelihood of survival in COVID-19, sepsis, and trauma patients.