Yes, there is now an FDA-cleared blood test for Alzheimer’s disease. In May 2025, the FDA cleared the first blood test designed to help diagnose Alzheimer’s by measuring two proteins in a standard blood draw. Before this, confirming Alzheimer’s required either a PET brain scan costing thousands of dollars or a spinal tap to collect cerebrospinal fluid.
What the Test Measures
The FDA-cleared test, called the Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio, works by measuring two proteins found in your blood plasma. One is a form of tau protein (pTau217) that increases when tau tangles build up in the brain. The other is a fragment of amyloid protein (β-amyloid 1-42) that decreases in the blood when amyloid plaques accumulate in brain tissue. The test calculates the ratio between these two proteins, and that ratio correlates with whether amyloid plaques, a hallmark of Alzheimer’s, are present in the brain.
Think of it as an indirect window into the brain. Rather than scanning for plaques directly, the test reads chemical signals in your blood that reliably reflect what’s happening inside brain tissue.
How Accurate It Is
In the clinical study used for FDA clearance, 91.7% of people who tested positive actually had amyloid plaques confirmed by PET scan or spinal fluid testing. Even more notably, 97.3% of people who tested negative were confirmed to be free of amyloid plaques. That high negative predictive value is especially useful: a negative result can give strong reassurance that Alzheimer’s pathology is not present.
Broader research on p-tau217 blood testing supports these numbers. In a study of people with early-onset or atypical dementia published in Neurology, the blood test outperformed FDG-PET (a type of brain metabolism scan) at identifying who had Alzheimer’s pathology. The blood test caught 91% of amyloid-positive cases compared to 70% for the PET scan, with fewer false alarms as well.
Who the Test Is For
The current FDA clearance is specifically for people who already have cognitive symptoms, meaning noticeable problems with memory, thinking, or daily functioning. It is not cleared for screening healthy people who have no symptoms. The 2024 diagnostic criteria from the National Institute on Aging and the Alzheimer’s Association explicitly recommend against diagnostic testing in cognitively unimpaired individuals outside of research studies, in part because no approved treatments currently target Alzheimer’s in people without symptoms.
In practice, the test is intended to help when a doctor is trying to figure out why someone is experiencing cognitive decline. Many conditions mimic Alzheimer’s, including depression, thyroid problems, vitamin deficiencies, and other forms of dementia. The blood test helps confirm or rule out Alzheimer’s as the cause, which matters for treatment decisions.
How Early It Can Detect Changes
Research from the National Institutes of Health found that elevated p-tau217 levels appear in the blood years or even decades before Alzheimer’s symptoms begin. A person whose p-tau217 became elevated at age 60 would typically develop symptoms about 20 years later. Someone whose levels rose at age 80 would develop symptoms after roughly 11 years. The gap shortens with age, but the biological signal precedes noticeable decline by a significant margin in all age groups.
This early detection window is one reason blood biomarkers have generated so much interest. Even though the test is currently cleared only for symptomatic patients, the underlying biology suggests these markers could eventually play a role in identifying people at risk long before memory problems appear.
Cost and Insurance Coverage
Before FDA clearance, several companies offered Alzheimer’s blood tests directly to consumers or through physicians, but patients had to pay out of pocket. Prices ranged from roughly $300 to $1,750 depending on the company and test. Without FDA clearance, insurers had no reason to cover them.
Now that the Lumipulse test has FDA clearance, Medicare and private insurance coverage is expected to follow. Once that happens, the test will likely become a standard part of the diagnostic workup for people being evaluated for cognitive decline. Until coverage is formally in place, you may still face out-of-pocket costs, so it’s worth checking with your insurer before ordering.
Factors That Can Affect Results
Kidney function is one important variable. Research from Vanderbilt University Medical Center found that even mild kidney impairment, which affects roughly one-third of older adults, can skew the levels of several Alzheimer’s blood biomarkers. The effect was most dramatic for a marker called neurofilament light chain, which lost its ability to predict cognitive changes in people with mild to moderate kidney disease. Other markers, including amyloid beta and phosphorylated tau, were also affected to varying degrees.
This doesn’t mean the test is useless for people with kidney problems, but it does mean results need to be interpreted carefully. A doctor who knows your kidney function can account for this when reading results. It’s one reason the Alzheimer’s Association recommends these tests be part of a comprehensive clinical assessment rather than used in isolation. A single blood test number, taken without context, can mislead.
How It Fits Into Diagnosis
The blood test does not diagnose Alzheimer’s on its own. It tells your doctor whether amyloid plaques are likely present in your brain, which is one piece of the puzzle. A full evaluation still involves cognitive testing, a medical history review, and sometimes brain imaging to rule out other causes like strokes or tumors.
What the blood test changes is the path to that diagnosis. Previously, confirming amyloid pathology required a PET scan (which can cost $5,000 or more and isn’t always accessible) or a lumbar puncture (which many patients are reluctant to undergo). A simple blood draw can now provide that confirmation in most cases, making the diagnostic process faster, less invasive, and more widely available, particularly for people in areas without access to specialized imaging centers.
The Alzheimer’s Association currently recommends that blood biomarker testing be conducted by qualified specialists as part of a memory disorder evaluation. Some guidelines suggest that primary care doctors could eventually order these tests, provided the tests meet a minimum threshold of 90% sensitivity and 85% specificity. As the technology becomes more established, access through general practitioners is expected to expand.