Yes, there are several tests for Alzheimer’s disease, and the options have expanded significantly in recent years. What was once a diagnosis made mainly through symptom observation and ruling out other causes can now be confirmed with biological markers found in blood, spinal fluid, and brain imaging. No single test works alone in every case, but the combination of tools available today can detect Alzheimer’s pathology years before major symptoms appear.
Blood Tests: The Newest Option
Blood tests for Alzheimer’s represent the biggest recent shift in diagnosis. These tests measure a protein called phosphorylated tau 217 (p-tau217), which rises in the blood when Alzheimer’s pathology is present in the brain. In a large meta-analysis, the p-tau217 blood test showed 82% sensitivity and 86% specificity for detecting amyloid plaque buildup, and 83% sensitivity and 83% specificity for detecting tau tangles. In practical terms, that means the test correctly identifies Alzheimer’s pathology in roughly 8 out of 10 people who have it, and correctly rules it out in about 8 or 9 out of 10 people who don’t.
The test involves a standard blood draw, making it far less invasive than a spinal tap or brain scan. One commercially available version, PrecivityAD2, is already used in clinical settings. However, insurance coverage remains a major gap. As of 2025, Medicare does not yet cover blood-based Alzheimer’s tests, though legislation has been introduced in Congress (the ASAP Act) that would require coverage of FDA-approved blood biomarker tests once they’re deemed safe and effective. Until that happens, you may face out-of-pocket costs.
Updated diagnostic criteria from the Alzheimer’s Association now recognize that an abnormal result on one of these “Core 1” biomarker tests, which include blood-based p-tau217, is sufficient to establish an Alzheimer’s diagnosis. This is a major change: the disease is increasingly defined by its biology rather than its symptoms alone.
Brain Imaging With PET Scans
PET scans offer the most direct look at Alzheimer’s pathology in a living brain. There are two types relevant to Alzheimer’s. Amyloid PET scans use specialized radioactive tracers to light up the amyloid plaques that are a hallmark of the disease. Three tracers are FDA-approved for this purpose. A separate tau PET scan uses its own FDA-approved tracer to detect the tangled tau proteins that spread as the disease progresses.
An amyloid PET scan can confirm whether plaques are present, which helps distinguish Alzheimer’s from other forms of dementia that look similar on the surface. A tau PET scan adds prognostic value: the more tau buildup visible, the more likely symptoms will worsen in the near term. These scans are highly accurate but expensive, often costing several thousand dollars, and not all facilities have the equipment. They’re typically reserved for cases where the diagnosis is uncertain or when a blood test result needs confirmation.
Spinal Fluid Analysis
A lumbar puncture (spinal tap) can measure Alzheimer’s biomarkers directly in the cerebrospinal fluid that surrounds the brain. The key markers are amyloid beta 42, amyloid beta 40, phosphorylated tau, and total tau. In Alzheimer’s, amyloid beta 42 drops (because the protein is getting trapped in plaques instead of flowing freely) while both forms of tau rise.
Clinicians look at specific ratios between these proteins rather than any single number. The ratio of p-tau to amyloid beta 42 and the ratio of amyloid beta 42 to amyloid beta 40 are both strong predictors of whether amyloid plaques would show up on a PET scan. Spinal fluid testing has been a reliable diagnostic tool for years and remains useful, especially in specialty memory clinics. The downside is the procedure itself: a needle is inserted into the lower back to collect fluid, which can cause a headache afterward and understandably makes many people hesitant.
Cognitive Screening Tests
Before any biomarker testing, most people first encounter a cognitive screening test in a doctor’s office. The two most common are the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). Both take about 10 to 15 minutes and involve tasks like remembering a short list of words, drawing a clock face, counting backward, or naming animals. These tests don’t diagnose Alzheimer’s on their own. What they do is measure whether your thinking and memory are performing below what’s expected for your age, which then guides whether further testing is needed.
Your doctor will also ask about specific changes in daily functioning: trouble remembering recent events, difficulty with planning or problem-solving, confusion about time or place, struggling to find words, or personality and mood shifts. They’ll often speak with a family member or close friend to get an outside perspective on how your cognition has changed over time. This clinical picture, combined with a screening score, determines the next steps.
Genetic Testing
Genetic testing is available but plays a limited role for most people. The gene most strongly linked to late-onset Alzheimer’s is APOE, which comes in three variants. The e4 variant increases risk: carrying one copy doubles or triples your chances of developing the disease, while the e3 variant (the most common) appears neutral and the e2 variant actually lowers risk. Direct-to-consumer DNA kits like 23andMe can report your APOE status.
That said, most experts don’t recommend routine APOE testing. The results can’t tell you whether you will or won’t get Alzheimer’s. Many people with e4 never develop the disease, and many without it do. Genetic testing is more useful in cases of early-onset Alzheimer’s (symptoms before age 65), where rare deterministic gene mutations, not just risk variants, can sometimes be identified. For the average person worried about memory, biomarker tests provide far more actionable information than a genetic report.
Who Should Get Tested
A formal diagnostic workup typically starts when you or someone close to you notices persistent changes in cognition that affect daily life. The warning signs that prompt evaluation include repeated trouble remembering recent events, difficulty concentrating or following plans, confusion about dates or familiar places, problems with language or vocabulary, poor judgment in decisions, withdrawal from social or work activities, and noticeable personality or mood changes like new depression or apathy. The key factor clinicians look for is a decline from your previous level of functioning, not just occasional forgetfulness.
Testing is also increasingly relevant for people without obvious symptoms. Because the updated diagnostic framework defines Alzheimer’s as a biological process that begins while people are still asymptomatic, biomarker testing can detect the disease at its earliest stage. This matters more now that disease-modifying treatments exist, since they work best when started early. If you have a strong family history or are considering enrolling in a clinical trial, early biomarker testing may be worth discussing with a specialist, even before memory complaints become obvious.
How These Tests Work Together
In practice, diagnosis usually follows a sequence. It starts with a clinical evaluation and cognitive screening. If those raise concern, a blood test for p-tau217 can serve as a first-line biomarker check. If the blood test is positive or inconclusive, a PET scan or spinal fluid analysis can confirm the findings with greater certainty. The newer diagnostic criteria describe this as a tiered system: Core 1 biomarkers (blood tests, spinal fluid, or amyloid PET) establish whether Alzheimer’s pathology is present, while Core 2 biomarkers (tau PET and additional fluid markers) help stage how far the disease has progressed and predict how quickly symptoms may advance.
This layered approach means most people won’t need every test. A clear blood test result combined with a clinical picture consistent with Alzheimer’s may be enough. More invasive or expensive tests get reserved for ambiguous cases or when treatment decisions require a higher level of diagnostic confidence.