Alzheimer's Disease: How It’s Diagnosed

Medically Reviewed by Jabeen Begum, MD on January 16, 2024
8 min read

Alzheimer’s disease isn’t part of normal aging. Some early signs may include trouble following a recipe you already know or paying your bills. You may suddenly have a hard time driving to a place you know well. You might get confused about what time it is or where you are. It may also be harder for you to follow conversations, or you may tell your friends or family the same thing you've already told them. You may sometimes forget an everyday word or use the wrong one.

If you think you or a loved one might be showing these or other signs of memory loss or other Alzheimer's symptoms, it’s important to see a doctor for testing. Your doctor can use tests to see how you're thinking. They also can look for signs of other behavior changes or trouble with your speech or decision-making. 

Remember that other conditions could lead to similar signs. Forgetting where you parked the car one day doesn't mean you have Alzheimer's. It's normal to forget things sometimes. Alzheimer’s also can have many of the same symptoms as other common conditions. Those include depression, vitamin deficiency, and taking medications that don’t work well together. A doctor can find out if your symptoms are happening because of Alzheimer’s or if it's something else that might be easier to treat.

Finding out you or a loved one has Alzheimer's is hard. But an early and accurate diagnosis can give you or your loved one time to plan for the future. You can start using some medicines that help people in the earlier stages of Alzheimer's control some of their symptoms, as well. You could explore other ways to keep yourself engaged or think about a clinical trial testing new treatments. You also can reach out through support groups to other people who are going through the same things.

The only way to get started on these as soon as you can is to see a doctor for thorough testing. Since there's no one test that can say if you have Alzheimer's, your doctor will use various ways to diagnose you. They'll check if you have signs of beta-amyloid plaques in your brain that are a hallmark of Alzheimer's. Medicines used to treat Alzheimer's work by getting rid of these plaques. Your testing may include:

  • Your medical history
  • Your mental status based on tests
  • Physical exams
  • Neurological exams
  • Blood tests
  • Tests of your cerebrospinal fluid (CSF)
  • Images of your brain

Your doctor will ask questions about your past and current health. They’ll want to know:

  • Your symptoms, including any trouble you have with everyday tasks
  • Other medical conditions you have now or had before
  • Medications you take
  • Your personal history, like your marital status, living conditions, employment, sexual history, and important life events
  • Your mental state. The doctor will ask you a series of questions that help them figure out if you’re having a mental health problem, like depression.
  • Family history, including any illnesses that run in the family

Your doctor will likely ask you other questions about your diet, nutrition, and whether you drink alcohol or use other substances. Be ready to answer questions such as:

  • What symptoms do you have?
  • When did they start?
  • What kinds of trouble are they causing in your everyday life?
  • How often does it happen?
  • Is it getting worse?




During your physical exam, your doctor will:

  • Check your blood pressure, temperature, and heart rate
  • Listen to your heart and lungs
  • Generally assess your overall health
  • Take any needed blood or urine samples for testing

These tests can help your doctor tell whether you may have something else that's causing symptoms that look similar to dementia. These may include:

  • Depression
  • Sleep apnea
  • Delirium
  • Side effects of medicine you're taking
  • Thyroid problems
  • Vitamin deficiencies
  • Drinking too much alcohol


Your doctor can also look for signs there's a problem with your brain for reasons other than Alzheimer's, including:

  • Stroke
  • Parkinson's disease
  • A brain tumor
  • Fluid in your brain
  • Any other condition that can cause problems with memory or thinking

Your doctor will check your:

  • Reflexes
  • Coordination
  • Strength
  • Muscle tone
  • Eye movements
  • Speech
  • Feelings or sensations

These tests can check for changes in your:

  • Problem-solving skills
  • Attention span
  • Counting skills
  • Memory
  • Thinking
  • Behavior

These tests will help your doctor know whether there are problems with the areas of your brain involved in learning, memory, thinking, or planning skills. Some tests you can take quickly. Others could take hours and may be complex. If you need more complete testing, you may need to see a doctor who specializes in evaluating people for:

  • Executive function
  • Judgment
  • Attention
  • Language

Overall, these tests will help your doctor know how problems in your thinking are affecting your ability to function normally. They'll check if you know what day or time it is and where you are. They'll see if you can remember lists of words, follow directions, or do simple math.

Your doctor may use different tests for this with different names including:

  • Ascertain Dementia 8 (AD8)
  • Functional Activities Questionnaire (FAQ)
  • Mini-Cog
  • Mini-Mental State Exam (MMSE)
  • Montreal Cognitive Assessment (MoCA)
  • Neuropsychiatric Inventory Questionnaire (NPI-Q)

Some electronic testing tools are now approved for cognitive testing, too. Ask your doctor which tests they recommend you take and why.

Screening you for depression and mood

Your doctor will also want to check how you're feeling in general. They'll look to see if you have signs of depression or a mood disorder. That's because depression and mood disorders can cause memory problems. They also can cause you to lose interest in things. Sometimes this can look like signs of dementia or Alzheimer's.

Your doctor may order tests to look at your brain. They mostly use these tests to see if there may be another reason for your symptoms. But scans may also show signs of Alzheimer's. Brain imaging can show:

  • Brain tumors
  • Signs of a stroke
  • Other brain injuries from trauma or infection
  • Fluid in your brain

Types of brain imaging

You could have different types of imaging tests to look at your brain. In CT (computed tomography), a machine takes X-rays of your body from many different angles very quickly. A computer turns the scans into a series of images that look like "slices" through the body. CT scans can show brain changes that are common in the later stages of Alzheimer's. For example, your doctor might check if parts of your brain have shrunk. To see this, they may need to compare new scans to ones that were taken before. 

MRI makes clear pictures of your body using a large magnet, radio waves, and a computer. It can help doctors see if a tumor or a stroke has caused symptoms that might look similar to Alzheimer’s. It also may help to show the brain changes that are linked to Alzheimer's. If you have a pacemaker, surgical clips, shrapnel, or other metal in your body, you won't be able to have an MRI. 

PET uses radioactive tracers to help map areas of your brain. It can measure how much energy your brain is using based on your brain chemistry. Some types of dementia can change the way your brain uses glucose for energy. Other types of PET scans can measure amyloid plaques that are associated with Alzheimer's. PET scans also can detect another protein, called tau, that makes tangles in your brain when you have Alzheimer's. 

Because of their cost, insurance doesn't usually cover PET scans to diagnose Alzheimer's. Researchers use amyloid PET scans and tau PET scans more often to help them figure out whether you're likely to get Alzheimer's in the future. This helps them test treatments in people before they have an Alzheimer's diagnosis.

It's now possible for your doctor to order a blood test to look for amyloid proteins in your body. But researchers are still working on finding ways to diagnose Alzheimer's with a blood test. For the most part, these tests aren't yet proven and available to most people outside of research.

Other tests look for signs of amyloid or tau proteins in your cerebrospinal fluid (CSF). CSF is a clear liquid. It surrounds and protects your brain and spinal cord. Doctors can look for proteins from your brain in it. To collect your CSF, a doctor will need to do a lumbar puncture. This test is also called a spinal tap. Your doctor may suggest this test to confirm that your symptoms are a sign of Alzheimer's. It's also possible it could detect changes earlier than tests that depend on changes in your thinking or behavior. 

You can find tests online that say they can test your memory and tell if you may have Alzheimer's. One example is a test for signs of dementia or Alzheimer's called the Self-Administered Gerocognitive Exam (SAGE). It was designed by researchers at The Ohio State University Wexner Medical Center, and it checks for memory or thinking problems that could be early signs of the disease.

You don't need any fancy equipment. Just pen, paper, and access to a computer so you can download the questions. It takes 15 minutes to finish. Some sample questions or tasks you might see on the test are:

  • How many nickels are in 60 cents?

  • If you buy groceries for $13.45, how much change would you receive back from a $20 bill?

  • Write down the names of 12 different animals.

  • Draw a large face of a clock and place two numbers on it in the right positions.

When you're done, you can take your answer sheet to your doctor so they can score it and talk to you about the results. Depending on your score, they may order follow-up tests or just keep it on file so they can see if there are any changes down the road.

Does the SAGE test work?

A 2010 study showed this test catches 79% of people with mild cognitive impairment (MCI). MCI is a change in memory and thinking skills that sometimes happens before a person has Alzheimer's. So the test is far from perfect. It can miss a lot of people who may be having early memory loss and may give you the wrong answer. 

But if you're worried about your memory, you might want to take it to see how you do. It may give you some information. If you're more comfortable taking a test at home, you could use it to look for changes over time by taking it more than once. A 2021 study testing SAGE found that it could tell when MCI was getting worse or progressing to dementia 6 months earlier than another test that doctors use. Your ability to take the test at home also could make it easier for you or others to access testing.  

Are online Alzheimer's tests all the same?

The short answer is no. One study looked at 16 online Alzheimer's tests to see how scientific, reliable, and ethical they were. The researchers rated 75% of them as "poor" or "very poor." No matter what your results are on any DIY test you take at home, it's a good idea to take any concerns you have about your memory to your doctor.

A word of caution on home screening tests

There's no approved test you can take at home to see if you have Alzheimer's. A test you take at home could say you've got Alzheimer's when you don't.  It also could say that you don't have it when you really do. While it's possible that a home test could give you useful information you could take to your doctor, you can't get an accurate Alzheimer's diagnosis at home. You'll need an exam and thorough testing from a doctor to get diagnosed and start treatment for Alzheimer's if you need it.