Yes, there are several tests for Alzheimer’s disease, and the options have expanded significantly in recent years. The FDA cleared the first blood test for Alzheimer’s in early 2025, and updated diagnostic guidelines now define the disease based on biological markers rather than symptoms alone. Depending on your situation, testing may involve a simple blood draw, brain imaging, spinal fluid analysis, cognitive screening, or some combination.
Blood Tests for Alzheimer’s
The newest and most accessible option is a blood test. The FDA-cleared test measures two proteins in your blood: a form of tau protein called p-tau217 and a fragment of amyloid called beta-amyloid 1-42. The ratio between these two proteins indicates whether amyloid plaques, a hallmark of Alzheimer’s, have built up in the brain.
The accuracy is strong. In the FDA’s clinical study, 91.7% of people who tested positive actually had amyloid plaques confirmed by a brain scan or spinal fluid test. Among those who tested negative, 97.3% truly were negative. A separate study of 427 people at Mayo Clinic found similar numbers: 92% sensitivity at the lower cutoff and 96% specificity at the upper cutoff, meaning the test catches most true cases while rarely flagging someone who doesn’t have the disease.
The test is designed for adults 55 and older who are already showing signs of cognitive problems. It’s not currently recommended for people without symptoms. Insurance coverage is still evolving. The FDA clearance opens the door for Medicare and private insurers to begin covering the cost, which should improve access over time. Until then, out-of-pocket costs may be a barrier for some patients.
Brain Imaging With PET Scans
Before blood tests became available, PET scans were the gold standard for detecting amyloid plaques in a living person. During the scan, a small amount of a radioactive tracer is injected into your bloodstream. This tracer binds specifically to amyloid protein clumps in the brain, lighting them up on the scan.
In a healthy brain, the tracer only shows up faintly in the brain’s white matter. In someone with Alzheimer’s pathology, tracer retention spreads into the outer layers of the brain, the neocortex. The earliest signal typically appears in regions toward the back and middle of the brain, and by the time someone has noticeable cognitive symptoms, the signal is usually widespread across the cortex.
PET scans remain highly accurate but are expensive, not available everywhere, and require specialized equipment. A newer type of PET scan can also detect tau protein tangles, the other signature protein of Alzheimer’s. Together, amyloid and tau PET scans give clinicians a detailed picture of what’s happening in the brain. In practice, though, the blood test may reduce how often PET scans are needed by serving as a reliable first step.
Spinal Fluid Analysis
A cerebrospinal fluid (CSF) test has been used for years to detect Alzheimer’s biomarkers. It involves a lumbar puncture, commonly called a spinal tap, where a small amount of fluid is drawn from the lower back. This fluid bathes the brain and spinal cord, so changes in its protein composition reflect what’s happening in brain tissue.
The test measures levels of beta-amyloid 42 and phosphorylated tau. In Alzheimer’s, beta-amyloid 42 drops in the spinal fluid (because it’s getting trapped in plaques in the brain rather than flowing freely) while tau levels rise. The FDA considers the blood test substantially equivalent to this CSF-based approach, which means for many patients the blood test can replace the spinal tap. CSF testing is still used when results from other tests are inconclusive or when greater precision is needed.
Cognitive Screening Tests
Biomarker tests detect the biological disease, but cognitive assessments measure how it’s actually affecting your thinking. The Montreal Cognitive Assessment, or MoCA, is one of the most widely used screening tools. It takes about 10 to 15 minutes and tests memory, attention, language, visual-spatial skills, and other mental functions.
Scoring is straightforward on a 30-point scale:
- 26 or higher: Normal cognition
- 18 to 25: Mild cognitive impairment
- 10 to 17: Moderate cognitive impairment
- Below 10: Severe cognitive impairment
A cognitive test alone can’t diagnose Alzheimer’s because many conditions cause memory problems, from depression and sleep disorders to vitamin deficiencies and other forms of dementia. But it’s often the first formal step. If your score suggests impairment, your doctor will typically recommend biomarker testing to determine whether Alzheimer’s is the cause.
Genetic Testing
Genetic testing plays a limited role in diagnosing Alzheimer’s. Most experts don’t recommend it for the common late-onset form of the disease because carrying a risk gene doesn’t mean you’ll develop Alzheimer’s, and not carrying one doesn’t mean you won’t.
The most well-known risk gene is APOE e4. Having one copy increases your risk; having two copies increases it further. But APOE testing has become more relevant for a specific reason: if you’re considering one of the newer antiamyloid therapies, carrying APOE e4 raises your risk of side effects from those treatments. In that context, genetic testing helps guide treatment decisions rather than diagnosis itself.
For early-onset Alzheimer’s, which strikes before age 65, genetic testing is more useful. Three specific gene mutations (in APP, PSEN1, and PSEN2) directly cause the disease when inherited. If you have symptoms of early-onset Alzheimer’s or a strong family history of it, testing for these mutations can provide a definitive answer and inform family planning.
How Diagnosis Works Now
The 2024 diagnostic criteria from the Alzheimer’s Association represent a major shift. Alzheimer’s is now defined as a biological disease, not a clinical syndrome. This means the diagnosis is based on measurable protein changes in the brain, not just on symptoms like memory loss. The disease is understood as a continuum: brain changes begin years before any symptoms appear and progress through stages of increasing severity.
In practice, testing is still recommended only for people who are already experiencing symptoms. The guidelines specifically advise against diagnostic testing in people without cognitive problems, outside of research studies. There are no approved treatments for asymptomatic individuals, so identifying the disease before symptoms begin doesn’t yet lead to actionable options in clinical care.
For someone with symptoms, the typical path starts with a cognitive screening, followed by one or more biomarker tests. The blood test is likely to become the most common next step given its accuracy and ease. If results are ambiguous, a PET scan or spinal fluid test may follow. The goal is to confirm whether Alzheimer’s biology is driving the symptoms, which matters more than ever now that disease-specific treatments exist.
Retinal Imaging: A Test in Development
Researchers are investigating whether a simple, noninvasive eye scan could detect signs of Alzheimer’s. The retina shares structural similarities with the brain, and studies suggest that changes in retinal blood vessels may mirror changes happening deeper in the nervous system. One ongoing study, running through 2026, is using a specialized imaging technique to map the structure and function of retinal blood vessels in people with mild cognitive impairment and Alzheimer’s compared to healthy controls. This approach is still experimental, but if validated, it could eventually offer a fast, low-cost screening tool available at an eye doctor’s office.