How is Alzheimer's disease diagnosed?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Alzheimer's disease can only be diagnosed with complete certainty after death using an autopsy. However, by questioning those affected and their family members, combined with using lab tests and brain scans, doctors are able to accurately diagnose Alzheimer's nine out of ten times. Using questions to determine someone's level of brain function can be very effective, as well as talking to family members about the symptoms being displayed.

Alzheimer's is difficult to diagnose because there are several causes of dementia, but blood tests can be used to narrow down the possible causes. Similarly, brain scans like magnetic resonance imaging (MRI) and computerized tomography (CT) can be used to look for visual clues.

Dr. Christine Ganzer
Geriatrics Nursing Specialist

A definitive diagnosis can only be achieved by conducting a biopsy of the brain but doctors can with good certainty determine whether or not the patient is suffering from Alzheimer’s through the use of tests.

Alzheimer's disease is diagnosed upon the exclusion of other neurodegenerative disease processes that may cause cognitive impairment or memory changes. The best way to be certain that the diagnosis is Alzheimer’s is to have some simple but specific tests that can be ordered by a qualified clinician that practices in the area of dementia. Typically these tests include neuropsychological testing that can localize areas of the brain where the deficits are occurring thereby helping the clinician identify other disease processes, blood tests that can eliminate deficiencies that can contribute to cognitive changes and Neuroimaging studies such as Positron Emission Tomography (PET) which can reveal abnormal cellular activity in the brain. Currently there are no cures for Alzheimer’s disease but there are medications such as Donepezil (Aricept), Rivastigmine (Exelon) and Memantine (Namenda) that have had some success in slowing down the disease process.


A healthcare provider will likely use a variety of methods to arrive at a diagnosis of Alzheimer's disease (AD). These diagnostic tools also help rule out other forms of dementia or health conditions that may produce dementia-like symptoms, such as alcohol abuse, blood vessel diseases, brain tumors, infections, medication interactions or side effects, mood disorders, neurological problems, thyroid disorders, or nutritional deficiencies.

Doctors may use the following diagnostic tools:

  • Evaluation of Symptoms. Healthcare providers rely on the patient and the patient's loved ones to provide a full description of symptoms, including what the patient is experiencing, when his or her symptoms began, and how frequently the symptoms occur.
  • Medical History. Full disclosure of a patient's past and current medical conditions and procedures, surgeries, and traumas, as well as a complete list of his or her medications, vitamins, herbs, and supplements is necessary to help narrow a diagnosis. Information about diet, lifestyle, and family history of disease also is important.
  • Physical Exam. A physical exam may include evaluation of the heart, lungs, and blood pressure. The neurological component of the exam will assess reflexes, coordination, muscle function, speech, physical sensation, and eye movement.
  • Psychological/Psychiatric Exam. Evaluation of emotional or mental conditions can help determine if an underlying mood disorder such as depression may contribute to symptoms.
  • Lab Tests. A healthcare provider may test samples of blood, urine, or spinal fluid to help rule out other conditions that may be responsible for symptoms.
  • Brain Scans. An MRI, CT scan, PET scan or other form of imaging helps healthcare providers detect any brain abnormalities that may indicate AD or other disorders.
  • Neuropsychological Tests or Mental Status Exam. These tests detect and assess impairments in memory, language, comprehension, and reasoning skills.

The only certain diagnosis for Alzheimer's disease cannot be done until after death, when evidence of plaques, tangles and shrinkage of the brain can be seen.

For living patients, doctors may test various bodily fluids, such as urine, blood and spinal fluid.

A doctor might also use a brain scan, such as MRI, PET or CT scan, to look for unusual formations in the brain.

An interview also can provide useful information about memory and other health issues. Some simple tests can also help find out more about the patient's attention span, counting abilities and short-term and long-term memory.

Most importantly, a doctor needs to rule out other potential causes for the patient's problems, such as other forms of dementia, cognitive impairments, minor strokes or other conditions that can produce symptoms similar to Alzheimer's.

Primary care doctors as well as neurologists, psychiatrists and geriatricians typically diagnose and treat Alzheimer's disease. An evaluation usually requires two or more visits of 30 minutes or more, plus testing. The diagnostic process includes a thorough medical history and family interview, including questions about your current mental and physical conditions with an emphasis on any noticeable physical, mental and emotional changes. The doctor will want to get information from someone who knows you well, since you may not recognize your own limitations or symptoms. A healthcare professional should also ask for a list of prescription drugs and take a family health history. Routine tests, such as blood work, blood pressure screening and urine tests, will be part of a comprehensive physical evaluation.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.