There’s no single test for Alzheimer’s. It can take time and an evaluation from a doctor to ensure a correct diagnosis.

Alzheimer’s disease is a complex illness to diagnose. Research is ongoing to understand better what causes it and how to reduce someone’s risk of developing Alzheimer’s later in life.

This is a condition that does not show up in a blood or sample test. An Alzheimer’s diagnosis involves a thorough evaluation of the symptoms.

Doctors may diagnose Alzheimer’s after a person presents with early symptoms. Testing and evaluation might also rule out other causes for these traits. Doctors can then determine the stage of Alzheimer’s from what those tests reveal.

Alzheimer’s disease is classified as a major neurocognitive disorder. Major neurocognitive disorder is a new term for dementia, introduced in 2013 in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5).

Diagnosing Alzheimer’s can be an essential step for people who may have this condition and the people in their families. Your doctor will perform a series of evaluations to check whether you or your a loved one is experiencing cognitive changes. Doctors typically:

  • assess symptoms
  • perform cognitive evaluations
  • rule out other possible causes or conditions

These evaluations can also help your doctor define the type of cognitive challenges you’re experiencing and whether Alzheimer’s might be the cause.

To begin the diagnosing process, your doctor might ask about your experience — either as someone who could have Alzheimer’s or as a loved one of the person being evaluated. These questions may cover:

  • changes in behavior, personality, and mental function
  • ability to complete daily tasks
  • medical history and overall health
  • diet and lifestyle
  • use of over-the-counter and prescription medications

After learning about your symptoms, your doctor will usually perform a series of tests. These tests are looking to assess a few objectives:

  • to see the level of mental challenge, change, or impairment
  • to rule out other causes of mental and behavioral changes
  • to scan for biological indicators of Alzheimer’s

These tests may include:

  • Mental health evaluation: to look for signs of depression or other conditions
  • Cognitive function tests: to examine memory, language, counting, attention, and problem-solving
  • Blood and urine tests: to look for other health conditions
  • Imaging tests and brain scans: MRI, CT, or positron emission tomography (PET) to see other potential symptom causes or to verify an Alzheimer’s diagnosis

Alzheimer’s can be a mysterious condition because there may not always be early warning signs or symptoms. The cause of Alzheimer’s is still being researched.

Early detection of Alzheimer’s disease can be challenging because many of the evaluations needed for a diagnosis rely on tracking brain function decline. By the time some people can be diagnosed with Alzheimer’s, substantial negative changes in the brain have occurred.

This is why early detection is such a critical goal for researchers. If Alzheimer’s could be diagnosed early, treatment or measures to slow its progress could begin long before symptoms and a substantial decline has started to appear.

The diagnostic guidelines for Alzheimer’s recognize three clinical stages:

  • Preclinical: Significant symptoms do not yet appear. There may be changes in the brain, like protein buildup, but these do not affect a person’s daily life.
  • Mild cognitive impairment: Symptoms may include problems with memory or thinking that are unusual for a person’s age and education. These symptoms do not prevent someone from living independently.
  • Alzheimer’s dementia: Symptoms like memory loss, word-loss, and differences in visual-spatial cognition cause a severe impact on a person’s life. Often, they are no longer able to live independently.

Although Alzheimer’s is a progressive disease, not everyone who experiences mild cognitive impairment will experience Alzheimer’s dementia.

Many factors contribute to a person’s unique experience with the condition, including how Alzheimer’s might affect them in their later years.

Diagnosing Alzheimer’s at the preclinical stage

At one time, an Alzheimer’s postmortem diagnosis was the only way to verify that the condition caused a person’s symptoms.

Now, as experts continue to learn more about the disease, there is hope that biological markers, such as beta-amyloid and tau levels, along with brain scans, could be an early indicator, but more research is still needed.

Researchers are actively investigating possible biomarkers, such as:

  • proteins in spinal fluid
  • changes in the brain visible on imaging
  • genetic differences

Early detection may eventually prevent or slow the progression of Alzheimer’s and ultimately extend a person’s level of brain functioning for as long as possible.

Specifically, early detection can give people time to make changes to avoid risk factors connected to the condition, such as:

Also, if Alzheimer’s is diagnosed early, there may be more treatment options, including medications available to delay the onset of the condition.

Early-onset Alzheimer’s

There is an important distinction to make between early detection and early-onset Alzheimer’s.

With early detection, a doctor gives an Alzheimer’s diagnosis before cognitive symptoms and impairment emerge. With early-onset Alzheimer’s, someone begins to fully experience symptoms and impairment much earlier than other people with Alzheimer’s.

Most people who receive a diagnosis of Alzheimer’s are over the age of 65. Sometimes, people live with an early-onset Alzheimer’s diagnosis beginning in their 40s or 50s.

Doctors don’t know precisely what causes early-onset Alzheimer’s, but for some people, there is a genetic link that may run in family.

Early signs of Alzheimer’s

It’s worth reaching out to your doctor if you begin to experience or are experiencing concerning signs that could signal a major neurocognitive disorder. Early signs of Alzheimer’s include:

  • memory loss that impacts daily living
  • trouble with planning or problem-solving, beyond making simple errors
  • difficulty completing familiar tasks
  • losing track of seasons, days, or time
  • challenges with conversation or loss of words
  • decrease in judgment
  • losing things with the inability to retrace steps
  • social withdrawal
  • mood and personality changes

Sometimes, it’s a person’s family who first notices these changes. If some or all of these early signs exist, a doctor may conduct further tests. If there is an Alzheimer’s diagnosis, they may also determine the clinical stage the person is experiencing.

Recent advancements in neuroimaging technology and biochemical analysis have made tests much more accurate when detecting Alzheimer’s. Still, because there is a possibility for error, doctors must also rely on the combined results of other tests and evaluations.

Doctors can also gain important information about your health and possibly confirm or rule out other causes for your symptoms. For example, if you’re experiencing memory changes, Alzheimer’s may not be the cause. Parkinson’s disease and side effects from some medications can also cause memory issues.

Doctors can also examine if another kind of major neurocognitive disorder (dementia) is present besides Alzheimer’s that might be the cause.

Alzheimer’s disease is the most common cause of major neurocognitive disorder. Before symptoms occur, this condition is hard to spot in its preclinical stage, but experts are actively researching biomarkers that can more accurately predict Alzheimer’s.

Doctors diagnose Alzheimer’s by listening to your experiences and symptoms. They combine that information with specific tests to rule out other conditions before confirming an Alzheimer’s diagnosis.

The experience of Alzheimer’s is unique to each person. Medications and lifestyle interventions may help delay Alzheimer’s onset, and people with the condition can live for many years after diagnosis.

If you or a loved one are experiencing symptoms of Alzheimer’s, you can reach out to the Alzheimer’s Association helpline for 24/7 support at 800-272-3900.

You can also visit Psych Central’s guide to finding mental health support.