Both diabetes mellitus and osteoporosis are increasing worldwide and are two of the most important causes of morbidity and mortality in older patients. Bone disease is a serious complication of diabetes. Patients with diabetes mellitus have an increased risk of falls and fracture, most notably at the hip. Whereas patients with T1DM have a low BMD, those with T2DM tend to have normal or even slightly elevated BMD. Patients with diabetes typically have low bone turnover with reduction in bone formation and increased bone resorption. The pathophysiological mechanisms underlying bone fragility in diabetes mellitus are complex. In T1DM low levels of insulin and IGF-1 may impair osteoblast function. In both T1DM and T2DM hyperglycaemia, and the accumulation of AGEs compromise collagen properties, release proinflammatory factors and adipokines from adipose tissue, and potentially alter the function of osteocytes. Furthermore, several antidiabetic drugs are known to affect bone metabolism and fracture risk. Diagnosis of bone disease in patients with diabetes is a challenge as current methods for fracture prediction such as BMD and FRAX underestimate fracture risk for patients with diabetes. Through advances in new technologies such as TBS and HR-pQCT, we can better assess the bone quality and fracture risk in this group of patients. Clinical management should focus on falls prevention strategies, avoidance of known risk factors, maintenance of good glycaemic control and bone protective intervention in individuals at high risk of fracture.