This case study analyzes a critical incident involving a patient, Mrs. Jones, admitted with flank pain, high pyrexia, and dysuria, with a history of type I diabetes mellitus and acute pyelonephritis. The assignment utilizes Levett-Jones' clinical reasoning cycle to examine the patient's condition, including symptoms such as hypotension, tachycardia, and hyperglycemia, and the progression to severe complications like sepsis. The analysis explores the patient's deteriorating condition, the nurse's observations, and the importance of clinical reasoning in identifying and addressing the issues. The assignment also reviews the pathophysiology, diagnosis, and management of acute pyelonephritis, referencing relevant literature and research, including the study by Kumar et al. (2014) and the study by Eliakim-Raz, Yahav, Paul and Leibovici (2013). Furthermore, it discusses the use of antibiotics and the impact of glycemic control on patient outcomes. The paper concludes by emphasizing the nursing considerations and the importance of applying research findings to improve patient care, especially in managing the complications of acute pyelonephritis and acute kidney injury.