How Is Dementia Diagnosed?

Written by Angela Nelson, Alicia Racelis, PhD
Medically Reviewed by Shruthi N, MD on February 19, 2025
7 min read

There's no single test to diagnose dementia; it’s a process. You may go through several types of tests. The tests look at how your brain thinks or reasons (cognitive tests), functions (neurological tests), and works (brain scans). Then, your doctor will review all the information to see if a dementia diagnosis is likely.

Medication and physical therapy can help treat some dementia symptoms. So, it helps to find out what causes your symptoms sooner rather than later. Early dementia diagnosis helps you plan for the future. It can also make health care, financial, living, or legal decisions easier. 

A prompt diagnosis can give you more time to build a good relationship with doctors and caregivers. Your regular doctor might work with you to figure out what’s causing your dementia symptoms. They may also refer you to one or more of these doctors for certain tests:

  • A neurologist, who specializes in the brain and nervous system
  • A psychiatrist 
  • A psychologist or a neuropsychologist, who specializes in memory and mental functions
  • Another mental health specialist
  • A geriatrician, who specializes in the care of older adults

Your regular doctor probably will start with a physical exam and ask questions about your medical history, such as:

  • Does dementia run in your family?
  • When did the symptoms start?
  • Have you noticed changes in behavior or personality?
  • Do you have any other medical problems, or are you taking any medications?

People with dementia aren't always aware of their condition. So your doctor will ask someone close to you, like a friend or family member, those same questions.

Your doctor will gather information from many different types of tests to diagnose dementia. There isn't just one test. You'll take tests to see how your memory (cognitive), brain function (neurological), and brain structure (brain scans) works. 

Your doctor will also do blood tests and ask you questions about your mood. It's important to rule out and treat other medical conditions before diagnosing dementia. Your doctor will put all the test information together to see how likely it is that you have dementia.

Cognitive tests

These are a set of tasks to help your doctor see if you've got a problem with your memory, problem-solving, or language skills. These thinking, or cognitive, tests focus on your recall, counting, reasoning, and communication.

Your doctor may start with cognitive tests that measure your ability to think. There are a few different tests they can use to get a snapshot of your thinking abilities.

For example, they might ask you to draw a clock and mark the hands at a specific time. They may give you a short list of words to remember and repeat. You might also be asked to calculate numbers, like count backward from 100 by sevens.

Neurological tests

Your doctor will test your balance, reflexes, and eye movements to check how well your senses work.

To do this, they might ask you to push or pull their hands using your arms. You may also need to stand with your eyes closed and touch your nose. To check your reflexes, your doctor will use a small rubber hammer. They'll tap it against parts of your body and watch how you respond.

Lab tests 

To diagnose dementia, your doctor may run a special blood test. Depending on the type of test, it measures proteins in your blood like beta-amyloid or phosphorylated-tau217 (p-tau217). Blood tests help your doctor decide if an imaging study (like a PET scan) could detect amyloid plaques in your brain. 

Beta-amyloid can clump together in your brain to form amyloid plaques. And p-tau217 can tangle up the nerve fibers in your brain. Both plaques and tangles can slow down the way your brain works. These problematic shapes in your brain can point to a possible Alzheimer's diagnosis.

A regular blood test can also find problems such as a lack of certain vitamins or a thyroid issue. These medical conditions can change how your brain works, too.

Brain scans

Your doctor may use one or more of these to get a closer look at your brain and how it's working. They also can help rule out other problems like bleeding, a stroke, or a brain tumor:

  • CT scan: Your doctor will take a series of X-rays and put them together to make a more complete picture.
  • MRI scan: This uses powerful magnets and radio waves to make close-up images of your brain and the tissue and nerves around it.
  • PET scan: This shows the activity in your brain and can be used to check for the amyloid protein, which can be a sign of Alzheimer's disease.

Psychiatric evaluation 

Your doctor will ask questions about your mood and sense of well-being. This helps see if depression or another mental health condition might be causing your symptoms.

They'll probably ask about any behaviors that are causing concern. Your doctor will ask when and how long the behavior happens. And they'll talk with you about your relationships. They'll ask about people close to you like your spouse, children, or friends.

There are different kinds of cognitive or memory tests used to check how your memory works. These tasks or questions help your doctor know more about how you solve problems. They'll also show signs of dementia such as problems with thinking, recall, or language.

Although these memory tests can't diagnose dementia alone, they'll help your doctor know if you have a memory problem. The tests screen for dementia and give your doctor a good place to start. 

Mini-Mental State Examination (MMSE)

This 30-point screening test looks at things such as your memory and ability to concentrate. You'll repeat words or fill in the date. You may also be asked to spell a word backward or perform simple calculations. If you score 23 or less, you'll likely get more testing to see if you have dementia.

Montreal Cognitive Assessment (MoCA)

This newer memory test also screens for dementia using a 30-point scale. It will ask you to name pictures of objects, recall lists of words, and draw pictures. 

You'll be asked about similar objects (problem solving) and the date, place, or time (your location). This test checks your ability to focus (attention), communicate (language), and how you remember words (memory). 

The MoCA also tests your executive skills or how you plan and organize. A score of 22 or lower may mean you'll get more testing for dementia.

SAGE test

The Self-administered Gerocognitive Examination (SAGE) is a dementia test you can do at home. You'll fill out this memory test using a pen, without help. It asks you questions about your memory problems and medical history. 

The SAGE test also includes tasks such as stating the date, naming objects, and drawing a clock at a specific time. You'll also copy pictures, do simple calculations, and put things in categories.

It's a good idea to put together the following for your first appointment:

  • A list of symptoms (include everything you're feeling, even if seems unrelated to dementia)
  • Any sources of major stress or recent life changes
  • A list of all medications you take, including vitamins and supplements, and their dosages
  • A list of any questions you have

Because treatment can help ease dementia symptoms, check for dementia early. But there isn't just one test, dementia diagnosis takes time. Your doctor will first rule out and treat other medical problems. Next, you'll take cognitive, neurological, lab, and imaging tests --- this can include CT, MRI, and PET scans. Then, your doctor collects the information to let you know if dementia is likely.

What can prevent dementia?

While you can't prevent dementia, you can take steps to reduce your risk. If you have high blood sugar or blood pressure, keep it in check. Other things can help, like:

  • Reaching and maintaining a healthy weight
  • Doing regular aerobic exercises and strength training
  • Keeping your mind active with activities such as learning new skills
  • Staying connected with others
  • Getting at least 7.5 hours of sleep each night
  • Avoiding alcohol and tobacco use
  • Trying to prevent falls to avoid injury to your head
  • Taking steps to protect your heart health and keeping your cholesterol levels in check
  • Treating any hearing or vision loss you have

Who is more susceptible to dementia? 

Things such as age, genetics, or Down syndrome can raise your risk for certain types of dementia like Alzheimer's. Other things that contribute to dementia include drinking a lot, late-life depression, high cholesterol, obesity, sleep apnea, and untreated hearing and vision loss. But treating these medical conditions can help slow down your dementia symptoms. 

What are the early signs of dementia?

Everyone can have different signs, but you may get some early ones such as:

  • Frequently forgetting things
  • Problems with concentrating, planning, or organizing things
  • Trouble communicating 
  • Not understanding what you see, such as misjudging distances
  • Confusion about where you are or what time it is
  • Difficulty with your moods, or personality changes

If you or a loved one has any signs for dementia, get medical help or ask your doctor.

At what age does dementia start?

It depends on the cause for your dementia. For example, if you have early-onset Alzheimer's, you can get signs around the age of 30. But late-onset Alzheimer's may not show up till you're 65 or older.

Is there any specific diet for people affected with dementia? 

There's no specific diet to help with dementia. But some studies suggest following a Mediterranean-style diet. This diet focuses on veggies, fruits, fish, healthy oils, fiber-rich whole grains, and nuts.