The diagnosis of dementia is a clinical diagnosis, based on information from different sources.

NICE guidance indicates that a diagnosis of dementia should be made following an appropriate clinical assessment by a clinician with knowledge of dementia (including an appropriate neurological examination and cognitive testing).22 Blood tests should be undertaken to exclude reversible causes of cognitive decline if these have not already been addressed. Neuropsychology testing can be considered if it is unclear:

  • whether the person has cognitive impairment or
  • whether the cognitive impairment is caused by dementia or
  • what the correct subtype diagnosis is.

Following a comprehensive assessment, as set out in section 3 of the guideline, further investigations can be considered to help rule out other causes in people presenting with cognitive decline, or to help diagnose dementia subtype in those with a diagnosis of dementia.

The following recommendation is reproduced from the NICE guideline on assessment, management and support for people living with dementia and their carers (NG97).22



Offer structural imaging to rule out reversible causes of cognitive decline and to assist with subtype diagnosis, unless dementia is well established and the subtype is clear.

Only consider further tests if:

  • it would help to diagnose a dementia subtype and
  • knowing more about the dementia subtype would change management.