Key takeaways:
It can be difficult to diagnose Alzheimer’s disease. There’s no single test that can detect the disease, and symptoms can overlap with other conditions.
Scientists developed a new test that measures levels of two proteins in the blood, which are higher in people with Alzheimer's. The FDA recently cleared the test for people ages 55 years and older with signs of the disease.
Current research suggests this blood test may help diagnose people with Alzheimer's more quickly and more accurately than current tests.
Alzheimer’s disease is a common condition in the U.S. More than 1 in 9 adults over the age of 65 have it.
People with Alzheimer's may have trouble with memory, decision-making, and other daily tasks. But the symptoms can easily be confused with memory changes that normally occur with age. For this reason, it can be difficult to diagnose Alzheimer’s, especially in earlier stages.
Fortunately, scientists have developed a new blood test that may be able to detect the condition sooner.
What is the new blood test for Alzheimer’s disease?
The FDA has cleared the first blood test to assist with Alzheimer’s disease diagnosis. This test is called the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio test. It measures two proteins in the blood that are typically higher in people with Alzheimer’s. The test calculates the ratio of these proteins, which is correlated to the presence or absence of amyloid plaques in the brain. These plaques are a hallmark sign of Alzheimer’s disease.
The test is for people ages 55 years and older who have signs and symptoms of Alzheimer’s disease. It’s not a screening test for healthy individuals.
How is Alzheimer’s disease diagnosed?
The blood test for Alzheimer’s disease is relatively new. So, before going over the specifics, it helps to understand how this condition is typically diagnosed.
It starts with observing someone’s symptoms. The early symptoms of Alzheimer’s can be hard to spot. It can also be hard to face the possibility that you or someone you know might have it. Family and friends often notice these signs first.
In addition to memory loss, people with Alzheimer’s may also experience:
Trouble with directions
Forgetting where they are
Problems with language
Changes in mood
Spending more time alone
Difficulty managing finances
Difficulty with planning
How do you diagnose dementia? It often takes time. Learn about the cognitive and memory tests used to diagnose dementia.
How to talk to someone just diagnosed with Alzheimer’s: It can be hard to know the best way to be supportive. An expert explains what to say and what not to say to someone with a decent diagnosis.
Is it a ‘senior moment’ or dementia? Memory lapses are normal as you get older. Here’s how to tell the difference between normal aging and dementia.
If your loved one has symptoms of dementia, their primary care provider can perform a series of tests that can help figure out if they could have Alzheimer’s. These include:
Cognitive tests: Cognitive tests usually include a series of questions and tasks to help evaluate your thinking.
Blood and urine tests: These tests can help rule out other conditions, like electrolyte imbalance or a urinary tract infection (UTI), which can cause confusion in older adults.
Imaging tests of the brain: Brain imaging can help rule out other causes of the symptoms.
These test results can provide important information about your health. But it can still be hard for a primary care provider to know for sure whether you have dementia. There’s no single test that detects Alzheimer's with 100% certainty, so healthcare professionals use other tests to help.
How does an Alzheimer’s blood test work?
Alzheimer’s disease is caused by changes in the way cells in the brain talk to each other. Scientists believe that abnormal levels of proteins — called beta-amyloid and tau — cause this to happen. Everyone has these proteins in their body, but levels are higher in people with Alzheimer’s.
There are a few tests that healthcare professionals can use to measure levels of these proteins:
Lumbar puncture: This is often referred to as a spinal tap. It’s a procedure that uses a thin needle to collect a sample of fluid from the area around the spinal cord.
PET scan: This is an imaging technique that scans your brain. It’s similar to getting an MRI.
Blood test: This is a newer type of test that measures levels of the beta-amyloid and tau proteins in the blood.
The blood test is a faster, easier way to measure these proteins. Spinal taps and PET scan tests are a bit more involved. And they can’t be performed in a regular healthcare office. This can also delay the time it takes to get results.
How accurate is blood testing for Alzheimer's disease?
Any test that’s used to diagnose a condition, including Alzheimer’s disease, needs to be accurate to make sure the diagnosis is reliable.
A clinical study evaluated the new blood test in over 1,000 older adults. The blood test detected Alzheimer’s disease with about 90% accuracy, which is very high. In comparison, standard methods used to diagnose Alzheimer's are about 60% to 70% accurate. Since these other tests are less accurate, they may miss a diagnosis.
FDA experts used a different data set for the approval process for the new blood test. They reported high accuracy, at almost 92%. Negative results were confirmed in 97% of cases, which means this test has a low probability of giving false negative results. About 20% of tests were inconclusive.
What does it mean if the test is positive or negative?
For someone with symptoms of Alzheimer’s, a positive test likely means they have the condition. A negative test indicates that Alzheimer’s is unlikely, but it doesn’t rule it out entirely. A primary care provider or dementia specialist will use the test results in combination with other factors (as noted above) to make a diagnosis. They can help you and your loved one determine the best next steps after the blood test.
Why is this test important?
Having a blood test for Alzheimer’s disease is important for a few reasons:
It’s more accessible to people than a PET scan or lumbar puncture.
It’s also cheaper and with faster results.
It’s less invasive than a lumbar puncture.
It makes it easier for researchers to monitor people in clinical trials.
Scientists hope that this new blood test can be used to diagnose adults with Alzheimer’s more quickly and accurately than current methods. An earlier diagnosis means that people with Alzheimer's can be treated sooner. It may also help researchers discover new therapies.
Frequently asked questions
The blood test can be performed at some outpatient offices and most large commercial laboratories. You’ll need an order for the test before you go.
Because the test is new, it’s best to check with your healthcare team or the lab before committing to the test. There’s no official policy yet regarding Medicare coverage.
The blood test can be performed at some outpatient offices and most large commercial laboratories. You’ll need an order for the test before you go.
Because the test is new, it’s best to check with your healthcare team or the lab before committing to the test. There’s no official policy yet regarding Medicare coverage.
The bottom line
For many years, scientists have worked hard to find a test that can accurately diagnose Alzheimer’s disease. The FDA has cleared a new blood test that can help detect Alzheimer’s more quickly and accurately than previous methods. But it’s not for everyone. Your healthcare team will likely use it as part of their diagnostic process. Experts expect that this new test will help people with Alzheimer’s start treatment earlier, and it'll help to improve research on treatments.
Why trust our experts?
References
Alzheimer’s Association. (n.d.). Alzheimer's disease facts and figures.
Colarossi, J., et al. (2025). What a newly approved blood test means for diagnosing Alzheimer’s. The Brink.
Fisher Center for Alzheimer’s Research Foundation. (2025). What to know about the new blood test for Alzheimer’s.
National Institute on Aging. (2024). What happens to the brain in Alzheimer's disease? National Institutes of Health.
Palmqvist, S., et al. (2024). Blood biomarkers to detect Alzheimer disease in primary care and secondary care. JAMA.
U.S. Food and Drug Administration. (2025). FDA clears first blood test used in diagnosing Alzheimer’s disease.
