Highlights (a) Why did we undertake this study? Stress hyperglycemia is classic but a long-overlooked pathophysiological process and a recently validated parameter, stress hyperglycemia ratio (SHR), facilitates its estimation. (b) What is the specific question(s) we wanted to answer? Is SHR associated with the in-hospital prognosis in non-surgical patients with type 2 diabetes and heart failure? (iii) What did we find? Compared to the nadir range of SHR at 0.79 to 1.08, both high and low SHR at admission elicit elevated risks of cardiac, kidney, and infectious adverse events during hospitalization in non-surgical patients with type 2 diabetes and heart failure. (iv) What are the implications of our findings? Clinicians should understand the inconsistency between the blood glucose at admission and HbA1c indicates poor prognosis during hospitalization and warrants additional monitoring.