People who are concerned about a decline in cognitive function, including memory loss or unusual changes in mood or behavior should consult their physician as soon as possible. Diagnosis will usually begin with a medical history and a physical examination. People are encouraged to keep a log of their symptoms to report to their physician. A physician may also ask family members or close friends about the nature of the patient’s symptoms. During the medical history, the physician may ask questions related to the patient’s dietary habits and use of alcohol in order to establish potential causes of dementia that can be reversible. During the physical examination, the physician will likely assess neurological function by testing the patient’s reflexes, balance and coordination.

A physician may conduct a mental status examination to assess the patient’s stage of dementia. During the exam, the physician may ask the patient a variety of questions aimed at testing the patient’s awareness of surroundings, problem solving skills and memory skills. Examples of items on the test may include:

• Situational questions such as “What year is it?” or “What is the address of this office?”
  
  
• Remembering and recalling a short list of items (e.g. a ball, a pencil, a dog)
  
  
• Counting backwards or spelling a word backwards
  
  
• Naming familiar objects in the room as the physician points to them
  
  
• Following simple instructions or writing a simple sentence

This test can also be used after diagnosis to evaluate the progression of dementia in the patient.

Additionally, blood and urine tests may be performed to test for conditions that cause dementia. These may include tests for vitamin deficiencies, poisoning or infections. A sample of spinal fluid may also be taken using a spinal tap to test for infections of the brain or spine.

Imaging tests, such as magnetic resonance imaging (MRI) tests and computed axial tomography (CAT) scans may be used to identify signs of brain abnormalities that may be the result of injury, stroke or a tumor. This enables physicians to identify the underlying cause of the dementia or to take steps towards preventing potential causes of dementia (e.g. strokes). However, imaging tests have limitations and are unable to identify many of the brain abnormalities that are the hallmark of progressive dementias such as the plaques and tangles of Alzheimer's disease and the Lewy bodies of Lewy body dementia.