The diagnosis of diabetes mellitus impairs the skeleton and represents a risk factor for osteoporotic fractures. The underlying mechanisms are not fully understood, but may include direct and indirect effects of chronic hyperglycemia on the skeleton. In general, bone metabolism is more severely affected in type 1 diabetes mellitus (T1DM) as compared to type 2 diabetes mellitus (T2DM), especially in the presence of diabetic complications. Bone mass may even be high or normal in patients with T2DM, but this does not confer protection against fractures as a result of reduced bone quality. Glitazones used as oral antidiabetic drugs promote bone loss and should not be used in patients with osteoporosis. A physically active lifestyle with healthy nutrition, including adequate uptake of calcium and vitamin D, along with comprehensive prevention of diabetic complications, represent basic therapeutic measures. Identification of risk factors, assessment of bone mineral density, and laboratory tests help to develop an individualized specific treatment plan. In patients with diabetes mellitus, all established osteoporosis drugs seem to be effective.