Further Investigations: Tests and Imaging

There are no specific tests for the diagnosis of Alzheimer's disease.

Therefore, the principle is to rule out other conditions and to diagnose Alzheimer's by exclusion.

Initial Investigations

Initially, blood tests are performed to exclude anaemia, kidney or liver problems, hypothyroidism, vitamin deficiency and infection. A chest x-ray and urine analysis may also be carried out.

In some cases, further investigations such as a drug screen or HIV test may be necessary.

Brain imaging

Brain imaging is recommended for any recent dementia.

Computerised Tomography (CT)

The first imaging technique would be a CT scan.

CT is useful to show any thinning of brain tissue, brain tumours or hydrocephalus (excess fluid around the brain).

Magnetic Resonance Imaging (MRI)

  • MRI is preferred to CT and generally required when diagnosis is uncertain
  • MRI offers a more detailed scan so that any loss of brain tissue associated with Alzheimer's disease can be seen
  • Therefore, MRI can highlight very early anomalies before people will develop the disease
  • MRI also enables doctors to follow the disease's progress


When a diagnosis of dementia is more difficult, a Single Photon Emission Computed Tomography (SPECT) or a Positron Emission Tomography (PET) is recommended.