Diagnosing Lewy Body Dementia: Tests Doctors Use and Next Steps After an LBD Diagnosis

Medically Reviewed By Shilpa Amin, M.D., CAQ, FAAFP

There is no definitive test to diagnose Lewy body dementia (LBD). Doctors use a range of tests to help them reach an LBD diagnosis, such as blood tests, brain scans, and a neurological assessment.  The only way to confirm a Lewy body dementia (LBD) diagnosis is through an autopsy of the brain after death. However, experts are researching ways to diagnose LBD more accurately during the course of the disease.

This article explains how doctors make a diagnosis of LBD, including tests and evaluations. It also discusses symptoms that could indicate LBD and the next steps after an LBD diagnosis.

How do doctors diagnose Lewy body dementia?

Illustration of doctor shining light on brain scan to portray Lewy body dementia diagnosis
Illustration by Maya Chastain

Some early symptoms of LBD, such as cognitive changes or hallucinations, can also be symptoms of other underlying conditions. As a result, doctors will likely first rule out other possible causes before diagnosing LBD.

According to the National Institute on Aging (NIA) Trusted Source National Institute on Aging Governmental authority Go to source , doctors typically perform a physical exam. They will want to see whether you have treatable symptoms or a condition that interferes with your cognitive function.

They may measure your blood pressure and order lab tests to check your hormone levels. 

Your physician may also ask about your medical history and whether you have a family history of dementia. They may also ask about your symptoms and any changes in your ability to carry out daily tasks.

Doctors often also perform a series of tests to help inform a diagnosis of LBD.

Learn more about early signs of Lewy body dementia.

What tests can help diagnose Lewy body dementia?

Right now, there is no definitive test for LBD other than a brain autopsy after death. However, researchers are conducting a clinical trial into a possible diagnostic test for LBD and other similar diseases.

The NIA Trusted Source National Institute on Aging Governmental authority Go to source explains that researchers are also studying the use of imaging, genetic, and blood tests for LBD diagnosis earlier during the disease. 

Currently, specialists use multiple tests to rule out other conditions and help them reach a diagnosis of LBD. These include the following.

Neurological exam

A neurological exam helps neurologists identify symptoms affecting your nervous system

The Lewy Body Dementia Association explains that during a neurological exam, doctors test for factors that include:

  • balance and gait
  • speech and communication
  • eye movements
  • blood pressure, including possible changes when you sit or stand
  • involuntary movements or tremor
  • changes in senses, particularly touch or smell

A follow-up exam may take place after 6 months. However, if you or someone you know is experiencing worsening of symptoms, contact your doctor for a prompt evaluation.

Imaging tests

People with LBD symptoms may undergo one or more brain scans. These tests do not specifically diagnose the condition but can rule out other possible causes, such as a brain tumor or bleeding in the brain. 

Imaging exams may include Trusted Source National Institute on Aging Governmental authority Go to source

Blood and fluid tests

Blood and fluid tests can help doctors rule out infections or other conditions that can cause symptoms of dementia. These tests may include:

  • blood glucose test
  • urinalysis
  • thyroid hormone level measurement
  • kidney function evaluation
  • liver function evaluation
  • drug and alcohol screening
  • testing for infections that can cause dementia, such as syphilis or HIV
  • lumbar puncture, or spinal tap, to test spinal fluid

Sleep evaluation test

Some people with LBD have rapid eye movement (REM) sleep behavior disorder. This causes them to act out their dreams and perform dream-enacting behaviors, such as talking and kicking. 

If these symptoms are present, your healthcare professional may order a polysomnogram, a sleep study that tests for REM sleep behavior disorder

This test involves using sensors that monitor a person’s movement, breathing patterns, and heart activity while they sleep. 

Learn more about what happens during a sleep study.

Collectively, these tests can determine whether someone has what doctors call indicative biomarkers for LBD. Confirmation of these biomarkers can inform a formal LBD diagnosis.

What are the diagnostic criteria for Lewy body dementia?

In 2017, the Dementia with Lewy Bodies Consortium updated its criteria for diagnosing LBD. It classified the categories of diagnosis as probable LBD and possible LBD.

Probable LBD

To diagnose probable LBD, doctors must identify two or more core clinical features of the disease, regardless of whether they have indicative biomarkers.

These core clinical features include:

  • changes in cognitive ability, particularly attention and alertness
  • clear, recurring visual hallucinations
  • REM sleep behavior disorder
  • symptoms of parkinsonism, such as tremor, rigidity, or loss of mobility

If someone has confirmed biomarkers for LBD, then only one core clinical feature needs to be present to make an LBD diagnosis.

Possible LBD

If someone has no evidence of biomarkers and only one core clinical feature, a doctor may make a diagnosis of possible LBD.

This can also happen if someone does not have any core clinical features but tests positive for at least one indicative biomarker.

Learn more about other types of dementia.

When should you see a doctor for signs of Lewy body dementia?

At first, LBD may cause mild symptoms and you may not associate them with dementia. As the disease progresses, symptoms get worse. 

Consider contacting a doctor for a prompt evaluation if you or someone you know has signs of LBD, especially if they are age 65 years and older.

The earlier you can get an accurate diagnosis, the sooner you can begin treatment to manage the progression of symptoms.

LBD symptoms that should receive medical evaluation include:

Additional symptoms that may indicate LBD include:

What are the next steps after a Lewy body dementia diagnosis?

An LBD diagnosis can be challenging and emotional. Your doctor will discuss your individual diagnosis with you and help develop a treatment plan to manage symptoms.

The NIA Trusted Source National Institute on Aging Governmental authority Go to source provides a list of steps that can help you and your family prepare for the future and foster the highest possible quality of life now. These steps include:

  • Building a support network: Having a strong group of loved ones and caregivers can help provide logistical assistance while also offering an outlet for social or spiritual support.
  • Assuring physical safety: Make sure your home is clear of hazards that can cause falls or injury. Consider wearing a medical alert bracelet or subscribing to an emergency service that can help you call 911 if necessary.
  • Planning: While it may be difficult to think about, making personal or financial decisions early in your diagnosis can help ensure your wishes are met. Your medical team can provide guidance on developing a care plan and refer you to resources for financial and legal planning.
  • Participating in favorite activities: If possible, find time to enjoy the same hobbies and interests you had before your diagnosis. Spending time with friends and family can provide emotional support and help you better enjoy each day.

Learn more about treatments for Lewy body dementia.


There is no definitive test to diagnose Lewy body dementia (LBD). However, doctors can use a series of tests to rule out other conditions and reach a diagnosis of LBD.

These include cognitive evaluations, blood tests, imaging tests, and sleep evaluations. Based on these results and observations of core symptoms, doctors can determine a diagnosis of probable LBD or possible LBD.

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  1. 4 tips for people living with Lewy body dementia. (2021). https://www.nia.nih.gov/health/4-tips-people-living-lewy-body-dementia
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  7. What is dementia? Symptoms, types, and diagnosis. (2022). https://www.nia.nih.gov/health/what-is-dementia

Medical Reviewer: Shilpa Amin, M.D., CAQ, FAAFP
Last Review Date: 2023 Jan 26
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