Dementia usually develops slowly, with mild early symptoms, so diagnosing dementia in its early stages can be difficult. It is normally diagnosed initially by the most common symptoms, such as memory loss. The diagnosis can be confirmed with a careful physical and mental examination and simple memory and mental ability tests that check things such as the ability to read, write or calculate.

However, as different types of dementia have similar symptoms, it can be more difficult to diagnose the precise type or cause. Blood tests, X-rays, or a CT or MRI scan of the brain may be necessary to provide more information.

Further tests may be needed to make sure that the person does not have a condition which can produce symptoms similar to dementia, such as depression or a severe urine or chest infection.

As those with dementia are often unaware they have a problem, many people with dementia are brought to medical attention by a caring relative or friend.