Does dementia show up in a blood test?

Blood tests can reveal a huge amount about you. They’re often carried out at different stages of the dementia journey and for many different reasons. Find out the key information you need to know about the link between blood tests and dementia.

In a nutshell

If dementia could be detected via one simple blood test it could make diagnosis quicker and make what is a tough process a little simpler. Although a test isn’t currently available, scientists are making great progress and other blood tests, which might reveal more about certain symptoms or genetics, are being used – with good results.


Blood tests are carried out as part of the dementia diagnostic process. For example, your GP might give you a blood test to check your overall health and to rule out other conditions which might be causing you symptoms which are similar to dementia, such as thyroid problems or a vitamin B12 deficiency which can be a sign of pernicious anaemia.

Here’s the science

  • Blood is made up of a fluid called plasma which contains red blood cells, white blood cells, platelets and proteins. Red blood cells contain a chemical called haemoglobin. If you have a vitamin B12 deficiency a blood test could reveal that you have less red blood cells than normal, or that you have less haemoglobin.
  • Blood tests to reveal thyroid problems are called thyroid function tests and are carried out to check how well the thyroid gland is working. They do this by revealing hormone levels (hormones are chemicals which are released into the blood stream). Thyroid function tests measure levels of a hormone called TSH in your blood.


Blood tests are also used for genetic tests which can reveal, for example, if someone has the defective genes usually present in frontotemporal dementia (Pick’s disease) or young onset Alzheimer’s.

Here’s the science

  • Genetic blood tests look for abnormalities in DNA, particularly gene mutations which can cause permanent change to DNA. Mutations to some genes, such as the Tau gene or the PGRN gene are thought to increase the risk of developing frontotemporal dementia (sometimes called Pick’s disease). Three genes APP, PS1 and PS2 have been identified as causing early-onset Alzheimer’s.


There is also a blood test for a gene called APOE-e4 which can identify people at higher risk of developing late onset Alzheimer’s.

Here’s the science

  • The gene apolipoprotein E(APOE) comes in three forms, APOOE-e4 is one of these three and is associated with the higher risk of Alzheimer’s.


Research already indicates that a blood test could become a very reliable way to diagnose dementia.

Here’s the science

  • A build-up of abnormal proteins in the brain is already known to cause several types of dementia, including Alzheimer’s disease (the proteins are called amyloid-beta and tau) and dementia with Lewy bodies (the proteins are called alpha-synuclein). Initial research has revealed that these proteins also occur within the blood platelets of people with dementia. Therefore a blood test which could identify the proteins could diagnose dementia.

Good to know

British scientists have developed a blood test for Alzheimer’s which, in a trial of 1,148 elderly patients was found to be 88 per cent accurate in predicting who would develop the disease. Further studies on a large group – up to 10,000 people – are needed but they hope that the test could be available on the NHS within five years.

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