How Alzheimer's Disease Is Diagnosed

An accurate, early diagnosis of Alzheimer's disease allows appropriate treatment to begin sooner, which is why it's important to schedule an evaluation if you or someone you know is showing some of the signs and symptoms. The healthcare provider will do screening assessments as well as review symptoms and medical history, but may also consider imaging to rule out other possible explanations for what one is experiencing.

While you can't diagnose yourself or someone else with Alzheimer's disease, you can perform a clinically supported at-home check that may point to the possibility and give the practitioner useful information to use in their assessment.

Sometimes, an MRI Is Used to Help Diagnosis Alzheimer's
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Self-Checks/At-Home Testing

Try not to jump to conclusions about the first sign of forgetfulness. It's normal, from time to time, to forget where you put your glasses or to bring back a library book by its due date. Alzheimer's is not a minor episode of forgetfulness, nor is it a sudden change in cognition; rather, it's a gradual progression of symptoms over time.

Keep track of symptoms over the course of a few months. Consider asking a trusted family member or friend for input as well. When calling to make an appointment with your healthcare provider, briefly share your observations and ask for an evaluation for Alzheimer's and other kinds of dementia. Bring the list of symptoms and any questions you can think of to your practitioner.

The online Self-Administered Gerocognitive Exam (SAGE) can be downloaded and taken at home. This self-screening dementia tool has been scientifically evaluated and has demonstrated good results in accurately identifying cognitive deficits. A key part of ensuring its accuracy is bringing it to your healthcare provider for scoring and interpretation rather than doing so yourself.

Any at-home screening test should be followed up with an assessment by a medical professional. There are many direct-to-consumer tests that are not scientifically validated and may give inaccurate results.

Different kinds of healthcare providers can diagnose Alzheimer's disease. You can make an appointment with your primary care doctor or seek out a specialist such as a psychologist, geriatric psychiatrist, neurologist, neuropsychiatrist, or geropsychiatrist.

Some communities have specific programs that specialize in Alzheimer's testing and diagnosing, so check with your local Alzheimer's Association chapter for recommendations.

Clinical Evaluation

The healthcare provider will ask you to tell them about the symptoms you've experienced to determine if they are consistent with the symptoms of Alzheimer's disease. If you are attending the appointment along with and out of concern for a loved one, you may be asked about what you've witnessed as well.

The practitioner will also likely ask if there are other diagnosed health conditions or any additional symptoms. If you're at a new healthcare provider's office, they may request that medical records be sent from your/your loved one's primary care physician ahead of time so that they have a full account of this information.

Additionally, family history for different kinds of dementia and health conditions will likely be reviewed, as well as any current medications (prescription or over-the-counter), vitamins, and supplements being taken.

Labs and Tests

A definitive diagnosis of Alzheimer's disease cannot be made until after death if and when a brain autopsy is conducted. A healthcare provider can, however, diagnose Alzheimer's with reasonable certainty by conducting several tests that can eliminate other causes of confusion and memory loss and by seeing how one's symptoms align with those of Alzheimer's.

The following are often considered when diagnosing Alzheimer's disease.

Mental Status Exams

A mental status exam is often used to objectively evaluate cognitive functioning.

There are several screening tests to evaluate cognition, but one of the more common exams is the Mini Mental State Exam (MMSE). This exam tests different aspects of the ability of the brain, such as memory, calculation, orientation, and communication.

The clock-drawing test is often a part of other screening tests, such as some of the below. Simply drawing a clock with the numbers and hands set at a specific time can reveal problems with cognition.

Other tests done on those being evaluated include:

  • Mini-Cog: This is a three-item screening test combining recall and a clock-drawing test. It takes only a few minutes to administer.
  • Montreal Cognitive Assessment (MoCA): This is a brief screening test to determine quickly whether further workup is needed. It assesses several aspects of cognitive functions, including orientation, short-term memory, delayed recall, language abilities, abstraction, and attention. It also includes a clock-drawing test and the Trails B test of executive function.
  • Saint Louis University Mental Status Exam (SLUMS): This is an 11-item Alzheimer's screening test. It includes items such as naming animals and recognition of geometric figures.​
  • 7-Minute Screen (7MS): This screening test was designed to be more sensitive so it could be used for early detection of Alzheimer's disease and mild cognitive impairment. Its four elements include an enhanced cued recall test, orientation, verbal fluency, and the clock drawing test.
  • Short Blessed Test (Orientation-Memory-Concentration test): This test contains six items, including orientation, telling time, counting backward, saying the months of the year backward, and recalling a name and address given at the beginning of the test.

The Alzheimer's Disease Assessment Scale-Cognitive Subscale test (ADAS-Cog) is an 11-part test often used after diagnosis of Alzheimer's disease to assess the level of impairment. It focuses on attention, language, orientation, executive functioning, and memory skills.

Tests may also be given to caregivers and families. They include:

  • AD-8 Informant Interview: This eight-item questionnaire is given to caregivers or family of the person being evaluated. It takes only a few minutes and can be done at home, then brought to an appointment with the healthcare provider. The questions include whether there have been changes in judgment, interest in activities, repeating things, learning new skills, orientation, handling finances, and remembering appointments.
  • Neuropsychiatric Inventory (NPI): This test is given to caregivers to screen for Alzheimer's disease and assess problems often seen in that condition. There are questions for different types of behavior, with the caregiver rating the frequency, severity, and distress the symptom causes on numerical scales. The types of behavior include delusions, hallucinations, agitation, depression, anxiety, elation, apathy, disinhibition, irritability, motor disturbance, nighttime behaviors, and appetite.

Laboratory Tests

Some healthcare providers will order tests such as blood work or a urinalysis. These tests can screen for infections or other medical conditions that could hinder one's ability to think clearly. Infections can often cause increased confusion, especially in older adults, so it's important to eliminate these and other reversible conditions as a cause.

In the rare case that autosomal-dominant Alzheimer's disease is suspected of being present in the family, a genetic test is available.


Brain changes can also be observed through various imaging techniques, such as:

  • Computed tomography (CT) is a sophisticated type of X-ray that can show a stroke, tumor, or brain shrinkage.
  • Magnetic resonance imaging (MRI) gives a more detailed picture than the CT scan. But unlike CT, MRI cannot be performed on people who have metal in their body. The detailed scans can show where stroke or small areas of bleeding have occurred.
  • Positron emission tomography (PET) uses an injected low-level radioactive tracer to show how areas of the brain are functioning. The fluorodexoyglucose (FDG) PET can show where the brain has low metabolism that may match some forms of dementia. Amyloid PET scans look for the deposits of amyloid plaques that are typical of Alzheimer's disease. Tau PET scans are mostly used in research. These look for the tau protein tangles seen in Alzheimer's disease.

Differential Diagnoses

The diagnostic process should include an evaluation for reversible conditions that can mimic Alzheimer's disease. You or your loved one may fear that the symptoms are due to Alzheimer's when they could be the result of many other conditions, such as depression or delirium due to an infection that will improve with the right treatment.

Problems with memory may be diagnosed as mild cognitive impairment, in which the person has normal overall cognition and can still do their daily activities. There is a greater risk of dementia, but it is not inevitable.

Tests will also differentiate between Alzheimer's and other kinds of dementia such as:

Any significant, sudden change in someone's ability to think merits a call to a healthcare provider immediately, as this may be a sign of a treatable condition.

Frequently Asked Questions

  • How is Alzheimer’s disease diagnosed?

    Alzheimer’s is usually diagnosed based on a person’s behavior along with a review of their medical history and family history. The NINCDX-ADRDA Alzheimer’s Criteria specifies eight domains that must be impaired for a person to have Alzheimer's: memory, language, perceptual skills, attention, constructive abilities, orientation, problem-solving, and functional abilities. Cognitive tests are commonly used to measure the degree of cognitive impairment.

  • Do you have to have symptoms to be diagnosed with Alzheimer’s?

    Yes, although other tests may help support the diagnosis. PET scans may show brain abnormalities consistent with Alzheimer’s, although they have a low level of accuracy in people with mild cognitive impairment. There are also blood tests that can detect genes and proteins consistent with Alzheimer’s, although you can have these genes and proteins without having Alzheimer’s.

  • When do signs of Alzheimer’s become more noticeable?

    Alzheimer’s disease is often classified into seven stages, from stage 1 (no impairment) to stage 7 (severe decline). In stages 1 and 2, symptoms may not be seen or may be subtle and easily dismissed. It is usually by stage 3 that signs are more noticeable, such as forgetting something that has just been said, asking the same question over and over, or having trouble with routine tasks like paying bills or keeping appointments.

  • How accurate is an Alzheimer’s diagnosis?

    A diagnosis based solely on clinical features has an overall accuracy of around 74%. When diagnostic blood tests are added, including tests for amyloid and tau proteins, the accuracy is increased to 89%. The same applies when a PET scan is used with a clinical diagnosis, increasing the overall accuracy to around 89%.

  • How long can you live after an Alzheimer’s diagnosis?

    Some people have been known to live for 20 years or more after their diagnosis. But, on average, the course of the disease will run from four to eight years from the time of the diagnosis. A great many people with Alzheimer’s die due to aspiration pneumonia caused when the swallowing reflex is affected, allowing food and water to enter the lungs.

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Additional Reading

By Esther Heerema, MSW
Esther Heerema, MSW, shares practical tips gained from working with hundreds of people whose lives are touched by Alzheimer's disease and other kinds of dementia.