Demographic trends with longer life expectancy and a lifestyle characterized by low physical activity and high-energy food intake contribute to an increasing incidence of diabetes mellitus and osteoporosis. Diabetes mellitus is a risk factor for osteoporotic fractures. Patients with recent onset of type 1 diabetes mellitus may have impaired bone formation because of the absence of the anabolic effects of insulin and amylin, whereas in long-standing type 1 diabetes mellitus, vascular complications may account for low bone mass and increased fracture risk. Patients with type 2 diabetes mellitus display an increased fracture risk despite a higher BMD, which is mainly attributable to the increased risk of falling. Strategies to improve BMD and to prevent osteoporotic fractures in patients with type 1 diabetes mellitus may include optimal glycemic control and aggressive prevention and treatment of vascular complications. Patients with type 2 diabetes mellitus may additionally benefit from early visual assessment, regular exercise to improve muscle strength and balance, and specific measures for preventing falls.