Diagnosing Alzheimer's disease

Find out why it's important to diagnose Alzheimer's disease as soon as possible. 

Why is an Alzheimer's disease diagnosis important?

Anyone who is concerned that they may have Alzheimer’s disease (or any other form of dementia) should seek help from their GP. If someone does have dementia, an early diagnosis has many benefits:

  • it provides an explanation for the person’s symptoms
  • it gives access to treatment, advice and support
  • it allows them to prepare for the future and plan ahead.

Testing for Alzheimer's disease

There is no single test for Alzheimer’s disease. The GP will first need to rule out conditions that can have similar symptoms, such as infections, vitamin and thyroid deficiencies (from a blood test), depression and side effects of medication.

The doctor will also talk to the person, and where possible someone who knows them well, about their medical history and how their symptoms are affecting their life. The GP or a practice nurse may ask the person to do some tests of mental abilities.

The GP may feel able to make a diagnosis of Alzheimer’s at this stage. If not, they will generally refer the person to a specialist. This could be an old-age psychiatrist (who specialises in the mental health of older people) often based in a memory service. Or it might be a geriatrician (who specialises in the physical health of older people), a neurologist (who specialises in conditions of the brain and nervous system) or a general adult psychiatrist (who specialises in mental health in adults) in a hospital.

The specialist will assess the person’s symptoms, and how they developed, in more detail. In Alzheimer’s disease there will usually have been a gradual worsening of memory over several months. A family member may be more aware of these changes than the person with suspected Alzheimer’s is themselves.

The person’s memory, thinking and other mental abilities will also be assessed further with a pen-and-paper test. When someone with Alzheimer’s is tested, they will often forget things quite quickly. They will often not be able to recall them a few minutes later even when prompted.

The person may undergo a brain scan, which can show whether certain changes have taken place in the brain. There are a number of different types of brain scan. The most widely used are CT (computerised tomography) and MRI (magnetic resonance imaging).

A brain scan may rule out certain conditions such as stroke, tumour or a build-up of fluid inside the brain. These can have symptoms similar to those of Alzheimer’s. It may also clarify the type of dementia. In a person with early Alzheimer’s disease a brain scan may show that the hippocampus and surrounding brain tissue have shrunk.

The diagnosis should be communicated clearly to the person and usually also to those closest to them, along with a discussion about the next steps. 

Want to know more about assessment and diagnosis?

Read the process and benefits of assessing someone for possible dementia and then making and sharing a diagnosis.

Learn more