Around 50% of older people with diabetes are asymptomatic. When symptoms are present they are often nonspecific, patients may feel generally unwell, tired or lethargic. Classic osmotic symptoms are usually less prominent in older age because of an increased renal threshold for glucose, resulting in reduced polyuria, and impairment of thirst sensation, resulting in reduced polydipsia. Because of the complexity of diabetes in old age a comprehensive assessment is important at initial diagnosis, with the aim of preventing loss of autonomy and preserving independence. Diabetes should be diagnosed if fasting plasma glucose is > or = 7 mmol/L or 2 hour postprandial glucose > or = 11.1 mmol/L. In addition to traditional micro- and macrovascular complications seen in younger people, older people with diabetes are at risk of developing atypical complications or geriatric syndromes such as cognitive dysfunction, depression, disability, falls, persistent pain and urinary incontinence. Glycaemic targets should be individualised taking into consideration the patient's overall health and life expectancy. Older people may tolerate higher levels of blood glucose before they develop osmotic symptoms because of a higher renal threshold for glucose with increasing age. On the other hand, they may appear to tolerate lower levels of blood glucose because of diminished autonomic symptoms of hypoglycaemia. Older people with diabetes are twice as likely to develop Alzheimer's disease or vascular dementia as age-matched controls without diabetes.