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Tests and scans to diagnose dementia

Find out about the tests and scans you might have if you’re referred to a specialist.

Types of tests and scans

A specialist may use several different tests and scans to find out why you are noticing changes and whether it is dementia. These include:

  • mental ability tests can check your memory and thinking
  • brain scans can check for changes in the brain
  • blood tests can check for other health conditions that may be causing symptoms

Mental ability tests

The specialist will ask you to complete tests similar to those you have already done at your GP surgery. The specialist will see how you answer different types of questions, for example: 

  • using your memory to recall a list of items
  • factual information, for example about the time and place
  • interpreting shapes
  • solving problems

If you are having an appointment by video call, you can write answers on a piece of paper and hold this up to the screen to show the specialist.

You do not need to prepare for any tests. It’s understandable to want to do ‘well’ in the test, but it’s very important that your health professional understands how your mind is working. Feeling as relaxed as possible will help you to complete the test as well as you can.

These tests cannot be used on their own to diagnose dementia. But they can help the specialist work out the type of problem you may have, particularly in the early stages of your symptoms.

The assessment can also be used to compare with later tests you may do, to see if anything has changed.

Types of mental ability tests

There are different versions of these tests, which have different names.

The Mini-Mental State Examination (MMSE) used to be the most commonly used test. Other versions of this test include MoCA (Montreal Cognitive Assessment) and ACE-III. These tests have slightly different questions, but are all designed to check your mental abilities in the same way. 

Brain scans

Some people may have a scan to check for changes in the brain. Not everyone needs a scan, especially if it is already clear what is causing your symptoms.

Brain scans do not hurt, and you will not need time to recover. The health professional will explain what these different scans involve.

It can take a long time to get an appointment for a brain scan, so the specialist may give you a temporary diagnosis while you wait.

Your scan may not show any unusual changes in your brain. This could mean that you do not have dementia, but it does not rule it out completely. If your dementia is in an early stage, it may not be seen on the scan.

CT (computerised tomography) and MRI (magnetic resonance imaging) are the most common scans used to check for changes in the brain.

CT scans

CT scans can check for signs of stroke or a brain tumour. But they cannot provide detailed information about the structure of the brain.

MRI scans

MRI scans can help confirm the type of disease causing a person’s dementia. It can do this by showing: 

  • if blood vessels are damaged, which happens in vascular dementia
  • which parts of the brain are shrinking (getting smaller). This helps find out which type of dementia a person has, as different diseases that cause dementia affect different parts of the brain

The MRI machine can be very loud so you may be offered earplugs. You will also have to stay as still as you can.

If you are uncomfortable with loud noises, or have trouble staying still, you should discuss this with your doctor before your appointment.

SPECT or PET scan

If the result of your MRI or CT scan is not clear, you may have another type of scan called a SPECT scan or a PET scan. These scans can show if there are problems with the blood flow in the brain.

DAT scan

If the specialist thinks you could have dementia with Lewy bodies or Parkinson’s disease dementia, you may have a scan of the brain called a DAT scan. These scans involve the injection of liquid and special scanning equipment that can look at how the brain is working, rather than what it looks like.

Blood tests

The GP should request a sample of your blood (and sometimes urine) to send off for testing. This is to check for other conditions that could be causing your symptoms, such as thyroid problems or vitamin deficiencies. 

How we support you

Get advice and information, whether you are worried about your memory, waiting for a referral or already diagnosed.

  • Call our support line to speak to a trained adviser
  • Visit our online forum to hear from people in the same situation

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Last reviewed: December 2023

Next review: December 2025