The leading cause of death for people suffering from type 2 diabetes is heart disease. The ability of the diabetic heart to pump blood around the body is diminished. Although significant advances in health care and medical technologies have been made in recent times, the treatment of diabetic heart failure is hampered by a lack of understanding about the root causes of the disease. Using a patient-specific data-driven mathematical modelling approach, I will explore how a decline in the ability of the heart to supply energy to its tissues leads to diabetic heart failure. These findings hold the potential to identify new treatment approaches to improve the health of diabetic patients.