People with type 1 diabetes (T1DM) want to enjoy the benefits of sport and exercise, but management of diabetes in this context is complex. An understanding of the physiology of exercise in health, and particularly the control of fuel mobilization and metabolism, gives an idea of problems which may arise in managing diabetes for sport and exercise. Athletes with diabetes need to be advised on appropriate diet to maximize performance and reduce fatigue. Exercise in diabetes is complicated both by hypoglycaemia and hyperglycaemia in particular circumstances and explanations are advanced which can provide a theoretical underpinning for possible management strategies. Management strategies are proposed to improve glycaemic control and performance.