A 76-year-old man with heart failure symptoms was diagnosed with HFrEF and abnormal glucose metabolism. Initially, enalapril was started, which was switched to losartan, and the next day to ARNI (sacubitril/valsartan, 50mg twice daily). After 23 days, his heart function improved and glucose levels normalized without diabetes medication, suggesting ARNI may benefit both heart failure and insulin resistance.