A reasonably accurate diagnosis of dementia can be made by taking a careful history of the person's problem from a close relative or friend, together with an examination of the person's physical and mental status. There is, however, no simple test to make a diagnosis and dementia can only be confirmed with certainty by examining the brain at post mortem. When making a diagnosis, it is important to exclude other treatable conditions that cause memory loss such as depression, urinary infection, vitamin deficiency and brain tumour. An early diagnosis is helpful, because it: