Yes, there are several tests for Alzheimer’s disease, and the options have expanded significantly in recent years. Doctors now use a combination of cognitive screening, brain imaging, spinal fluid analysis, and, as of 2025, the first FDA-cleared blood test. No single test provides a definitive diagnosis on its own, but together these tools can identify Alzheimer’s with high accuracy, sometimes years before symptoms become severe.
Cognitive Screening: The Usual First Step
If you or a family member brings up memory concerns with a doctor, the first thing that typically happens is a brief cognitive screening test done right in the office. The two most common are the Mini-Mental State Exam (MMSE) and the Montreal Cognitive Assessment (MoCA). Both are scored out of 30 points, with scores of 26 or above considered normal.
The MoCA is generally better at catching earlier stages of decline because it tests more demanding tasks like drawing a clock or recalling a short list after a delay. The MMSE has been around longer and is widely used to track how cognition changes over time at follow-up visits. Neither test can confirm Alzheimer’s specifically. They measure whether cognitive impairment exists, not what’s causing it. A low score triggers further investigation.
The New Blood Test
The biggest recent development is a blood test that can detect the brain changes associated with Alzheimer’s. In early 2025, the FDA cleared the first blood test for this purpose, made by Fujirebio Diagnostics. It measures the ratio of two proteins in the blood: a form of tau called p-tau217 and a fragment of amyloid. The test is approved for adults 55 and older who are already showing signs of cognitive trouble.
As a standalone test, p-tau217 blood testing achieves about 81 percent accuracy in identifying people with amyloid plaques in the brain. When doctors confirm the blood test result with a follow-up PET scan, accuracy rises to 91 percent. This is a major shift. Previously, confirming Alzheimer’s biology required either a PET scan costing thousands of dollars or a spinal tap. A blood draw is faster, cheaper, and far more accessible, which means more people can get a clear answer earlier.
It’s worth noting that this test is designed for people already experiencing symptoms. Current diagnostic guidelines specifically recommend against testing cognitively healthy people outside of research settings, partly because no approved treatments exist yet for people without symptoms.
Brain Imaging With PET Scans
PET scans remain the gold standard for visualizing Alzheimer’s-related changes in a living brain. Two types are used, each looking for a different protein.
Amyloid PET scans detect the sticky amyloid plaques that build up between brain cells in Alzheimer’s. These plaques can appear 15 to 20 years before memory problems start, so a positive amyloid PET scan confirms that Alzheimer’s biology is present, even if symptoms are mild. Tau PET scans are newer and detect tau tangles, the other hallmark protein of the disease. Tau tangles track more closely with the severity of symptoms, so a tau PET scan helps doctors understand how far the disease has progressed.
Medicare covers amyloid PET scans under specific conditions, typically when the scan is needed to guide treatment decisions or when the patient is enrolled in an approved clinical study. Access and out-of-pocket costs vary, and wait times for specialist evaluation can be long. Research from the Alzheimer’s Society found that one in four people wait two years or more before seeking help for dementia symptoms, and specialist appointments add further delay.
Spinal Fluid Analysis
A lumbar puncture (spinal tap) can measure Alzheimer’s-related proteins directly in the cerebrospinal fluid that surrounds the brain. Doctors look at levels of amyloid-beta 42, total tau, and phosphorylated tau. In Alzheimer’s, amyloid levels in spinal fluid drop (because the protein is getting trapped in plaques rather than flowing freely), while tau levels rise.
The ratio between tau and amyloid-beta 42 is the key number. In healthy adults under 60, this ratio averages around 1.6. Ratios above 2.4 are considered abnormally high and signal increased risk. Spinal fluid testing has been highly accurate for years, but many patients and doctors prefer to avoid the procedure when a blood test or PET scan can provide similar information. It remains most useful when other test results are inconclusive.
Genetic Testing
A blood test can check for the APOE4 gene, the strongest known genetic risk factor for Alzheimer’s. About 25 percent of people carry one copy of this gene variant, and 2 to 3 percent carry two copies. Carrying two copies substantially raises your lifetime risk.
However, APOE4 testing is not diagnostic. Plenty of people with the gene never develop Alzheimer’s, and many people without it do. Genetic testing is most useful in research settings or for people with a strong family history who want to understand their personal risk profile. It does not tell you whether the disease process has started in your brain.
Why Multiple Tests Matter
One reason doctors use several tests together is that Alzheimer’s symptoms overlap heavily with other conditions. Lewy body dementia, for example, can look nearly identical to Alzheimer’s in its early stages, and it’s frequently misdiagnosed. Vascular dementia, frontotemporal dementia, depression, thyroid disorders, and medication side effects can all mimic Alzheimer’s symptoms. Blood work, brain imaging, and cognitive testing each rule out different possibilities.
The current diagnostic framework treats Alzheimer’s as a biological continuum. Changes in the brain begin long before a person notices anything wrong, then progress through stages of increasing severity. Biomarker tests (blood, PET, spinal fluid) detect the biology. Cognitive tests measure the functional impact. Combining both gives doctors a much clearer picture than either approach alone.
What Getting Tested Looks Like in Practice
For most people, the process starts with a primary care visit where you describe your concerns and complete a cognitive screening test. If results suggest impairment, you’ll likely be referred to a neurologist or memory clinic. There, you may get an MRI to check for strokes, tumors, or other structural problems. Blood work rules out thyroid issues, vitamin deficiencies, and infections that can affect thinking.
If Alzheimer’s is suspected, the next step is biomarker testing. With the new blood test now available, this may be as simple as another blood draw. If results are borderline or if your doctor needs more detail to guide treatment, a PET scan or spinal fluid analysis may follow. The entire process from first appointment to confirmed diagnosis can take weeks to months, depending on specialist availability in your area.
Early testing has become more important as new treatments targeting amyloid plaques have entered the market. These therapies work best in the earliest stages of the disease, which means identifying Alzheimer’s biology sooner gives you more treatment options than waiting until symptoms are advanced.