A routine blood test — the kind ordered at your annual physical to check cholesterol, blood sugar, and kidney function — cannot detect dementia. That standard panel has no mechanism for identifying the protein abnormalities that characterize Alzheimer’s disease or other forms of dementia. However, the landscape shifted significantly in 2025, when the FDA cleared two specialized blood-based biomarker tests that can aid in Alzheimer’s diagnosis. These are not routine tests, and they are not screening tools for healthy people, but their arrival marks a genuine turning point in how dementia is identified and how early that identification can happen.
The distinction matters enormously for families navigating a diagnosis. If your doctor ordered a basic metabolic panel or complete blood count and found nothing alarming, that result tells you nothing about your dementia risk. But if a specialist orders a phosphorylated tau blood test — now available and FDA-cleared — the picture can look very different. This article explains what the new tests are, how they work, who qualifies for them, what they can and cannot tell you, and what the research suggests about where this technology is headed.
Table of Contents
- What Does a Routine Blood Test Actually Check — and Why It Misses Dementia?
- The FDA-Cleared Blood Tests That Can Now Aid Alzheimer’s Diagnosis
- How These Tests Work — Tau Proteins, Amyloid, and What They Measure
- How Early Can These Tests Detect Dementia — and What That Means Practically
- Who Should Get a Blood Biomarker Test — and Who Should Not
- What the Alzheimer’s Society and Clinical Guidelines Say
- Where Blood Testing for Dementia Is Headed
- Conclusion
- Frequently Asked Questions
What Does a Routine Blood Test Actually Check — and Why It Misses Dementia?
A standard blood panel ordered at a general checkup typically includes a complete blood count, a comprehensive metabolic panel, a lipid panel, and sometimes thyroid function. These tests evaluate things like red and white blood cell counts, blood glucose, liver enzymes, kidney markers, and cholesterol levels. They are valuable for detecting anemia, diabetes, kidney disease, and metabolic disorders — conditions that can sometimes mimic or worsen cognitive symptoms — but none of these measurements have any direct relationship to the biological processes that drive Alzheimer’s disease or most other dementias. Dementia, particularly Alzheimer’s disease, is characterized at the cellular level by the accumulation of amyloid plaques and tau protein tangles in the brain. These abnormalities develop over years or even decades before symptoms become apparent. A basic blood panel has no way of detecting these proteins.
It is not a matter of the tests being imprecise — they are simply measuring entirely different things. Ordering a metabolic panel to look for Alzheimer’s would be like checking a tire’s air pressure to diagnose an engine problem. The instrument is not wrong; it is just looking at the wrong system entirely. This is why, for decades, definitive Alzheimer’s diagnosis required either a PET scan to image amyloid deposits in the brain, a lumbar puncture to analyze cerebrospinal fluid, or a postmortem brain examination. Those options are expensive, invasive, or simply too late to be useful. The new blood-based biomarker tests were developed specifically to fill this gap.
The FDA-Cleared Blood Tests That Can Now Aid Alzheimer’s Diagnosis
In May 2025, the FDA cleared Lumipulse, described by the Alzheimer’s Association as the first blood test approved as an aid in diagnosing Alzheimer’s disease. Lumipulse measures amyloid and tau proteins in the blood, offering a window into the biological signature of Alzheimer’s pathology without requiring a spinal tap or brain scan. Then in October 2025, the FDA cleared Roche’s Elecsys pTau181 — notable because it is specifically indicated for use in primary care settings, making it the only blood-based biomarker test cleared for that environment. Its purpose is to help rule out Alzheimer’s-related amyloid pathology, which is meaningfully different from confirming a diagnosis. It is worth being precise about what “cleared” means in this context and who these tests are for. Lumipulse, for example, is approved only for adults 50 and older who already have cognitive symptoms.
It is not a screening tool for healthy individuals who have no complaints. A 55-year-old who feels sharp and has no memory concerns would not qualify — nor would it be appropriate for them to request one. These tests exist to help clinicians evaluate patients who are already presenting with symptoms, not to identify dementia risk in the general population. However, even within that symptomatic population, blood tests alone do not deliver a definitive diagnosis. The Alzheimer’s Association is clear that blood biomarker tests are used alongside PET scans and clinical evaluation, not instead of them. A positive tau result shifts the probability that a patient’s symptoms are Alzheimer’s-related, but it is one piece of a larger clinical picture. That nuance matters when families are trying to understand what a test result actually means for their loved one.
How These Tests Work — Tau Proteins, Amyloid, and What They Measure
The new blood tests detect specific proteins that are associated with Alzheimer’s pathology: phosphorylated tau (abbreviated as p-tau, in variants p-tau217 and p-tau181), amyloid, and neurofilament light chain (NfL). Tau is a protein that normally helps stabilize neurons; in Alzheimer’s disease, it becomes abnormally phosphorylated and forms tangles that damage and kill brain cells. Amyloid forms the plaques associated with the disease. NfL is a marker of neuronal damage more broadly and can be elevated in several neurodegenerative conditions. Research published in the journal Nature Medicine reported that blood levels of a tau fragment called MTBR-tau243 reflected tau tangles in the brain with 92% accuracy — a figure that positions blood testing as a genuinely viable proxy for what previously required far more invasive procedures.
Washington University Medicine, which conducted that research, described it as a blood test that not only diagnoses Alzheimer’s but can also gauge the extent of dementia. That level of precision from a blood draw would have been considered implausible a decade ago. Also in development is a dried blood spot test — a minimally invasive finger-prick method — reported in Nature Medicine in 2025. This format could make testing more accessible in settings where venous blood draws are difficult, including home-based or remote care situations. That version is not yet cleared for clinical use, but it represents the direction the field is moving: toward faster, simpler, less burdensome ways of accessing meaningful biological information.
How Early Can These Tests Detect Dementia — and What That Means Practically
The predictive power of blood biomarker tests has generated some of the most striking findings in recent dementia research. In a Swedish cohort of more than 2,000 older adults, blood biomarkers predicted dementia onset up to 16 years before the disease began. A separate study, reported by ScienceDaily in April 2025, found that biomarkers in independently living older adults could predict dementia 10 years before diagnosis. These are not small margins — they suggest that the biological signature of Alzheimer’s becomes detectable in the blood long before a person has any awareness that something is wrong. The practical implications of this depend heavily on what medicine can actually do with an early warning. At present, treatment options for Alzheimer’s remain limited, and early detection only pays off if there are meaningful interventions available.
That equation is beginning to shift with the approval of drugs like lecanemab and donanemab, which are most effective when started early in the disease course. A biomarker test that identifies amyloid burden years before symptoms emerge could, in theory, allow treatment to begin at a point when it can do more good. But that model — screen broadly, intervene early — requires that all the pieces be in place: accessible testing, effective treatment, clear clinical protocols, and insurance coverage that makes the process financially viable. The tradeoff worth naming here is that early detection without adequate support infrastructure can cause harm. A person who learns they have elevated amyloid levels at 60 faces years of uncertainty about when or whether symptoms will develop, without guarantee of a treatment that will change their trajectory. The Alzheimer’s Association’s July 2025 clinical practice guideline on blood-based biomarkers for specialists was, in part, an attempt to give clinicians a framework for using these tests responsibly — not just technically, but ethically and practically.
Who Should Get a Blood Biomarker Test — and Who Should Not
The clearest candidates for these tests are adults over 50 who are already experiencing cognitive symptoms and whose physicians are trying to determine whether Alzheimer’s pathology is the underlying cause. In that context, a blood biomarker test can meaningfully inform the diagnostic workup, potentially replacing or reducing the need for a PET scan or lumbar puncture. The Roche Elecsys pTau181, being cleared for primary care, is particularly significant because it gives general practitioners a tool to either rule out Alzheimer’s amyloid pathology or flag patients who need specialist referral — without requiring access to a memory clinic first. The people who should not be seeking these tests are healthy individuals with no cognitive concerns who want to know their future risk. This is not simply a matter of test availability.
The Alzheimer’s Association explicitly notes that Lumipulse is not approved for screening in the general population. There are good reasons for that boundary: false positives can cause unnecessary alarm, the meaning of amyloid elevation in a fully asymptomatic person is not fully understood, and the psychological burden of knowing you may develop dementia years from now — without clear steps you can take — can be severe. Curiosity is understandable, but a clinical diagnostic test designed for symptomatic patients is not the right tool for satisfying it. A warning worth emphasizing for caregivers and families: the existence of these tests does not mean that every memory lapse or moment of confusion warrants a biomarker workup. Normal age-related cognitive changes and dementia are not the same thing. Physicians evaluating whether a blood biomarker test is appropriate will first conduct a clinical assessment, review medications that might affect cognition, and rule out reversible causes — thyroid dysfunction, vitamin B12 deficiency, depression, sleep apnea — before moving to specialized testing.
What the Alzheimer’s Society and Clinical Guidelines Say
The Alzheimer’s Society in the United Kingdom has described blood biomarker tests as having the potential to revolutionize dementia diagnosis, while also noting clearly that they are not yet standard in routine care. That framing captures the current state accurately: the science is real and the tests are cleared for specific uses, but the infrastructure to deploy them widely — in primary care offices, with trained staff, covered by insurance, with appropriate counseling attached — does not yet exist at scale. The Alzheimer’s Association’s first clinical practice guideline on blood-based biomarkers, released in July 2025 for use by specialists, was a step toward building that infrastructure, but guidelines take time to change practice patterns on the ground.
In July 2025, the Alzheimer’s Association also convened the Alzheimer’s Association International Conference (AAIC), where the guideline was released and discussed. Its focus on specialists, rather than primary care, reflects where the evidence and the clinical experience currently sit. As familiarity with interpreting biomarker results grows and as more data accumulates from real-world use, those guidelines are expected to evolve.
Where Blood Testing for Dementia Is Headed
The trajectory here is clear, even if the timeline is not. Blood-based biomarker tests for Alzheimer’s will become more accurate, more accessible, and more integrated into routine clinical care over the next decade. The finger-prick dried blood spot method under development would remove one of the remaining barriers — the requirement for a venous blood draw in a clinical setting. Research into additional biomarkers may eventually allow blood tests to distinguish between different types of dementia, not just flag Alzheimer’s-related pathology.
And as treatments improve, the value of identifying disease early will only increase. What is already true, as of 2025, is that a blood test for Alzheimer’s is no longer a hypothetical. It exists, it is FDA-cleared, it is being used in clinical practice, and it is producing meaningful results. The gap between that reality and the routine care that most people receive is still significant, but it is narrowing. Families and clinicians who understand what these tests can and cannot do are better positioned to use them well.
Conclusion
A standard routine blood test cannot detect dementia. Complete blood counts and metabolic panels measure nothing related to the amyloid plaques and tau tangles that define Alzheimer’s disease at the biological level. That has been true for decades, and it remains true. What changed in 2025 is that two specialized blood-based biomarker tests — Lumipulse and Roche’s Elecsys pTau181 — received FDA clearance as aids in Alzheimer’s diagnosis, giving clinicians a tool that is less invasive than a PET scan and more accessible than a lumbar puncture.
These tests are meaningful, but they are designed for symptomatic adults being evaluated by physicians, not for general population screening. For anyone concerned about cognitive changes in themselves or a family member, the right first step remains a conversation with a physician — not a search for a self-ordered blood test. A clinician can assess whether symptoms warrant investigation, rule out reversible causes, and determine whether a biomarker test is appropriate and available. The science is advancing faster than most people realize. Understanding the difference between what a routine panel can tell you and what these new specialized tests can tell you is, at minimum, a way to ask better questions and get more useful answers.
Frequently Asked Questions
Can a regular blood test at my annual physical detect Alzheimer’s disease?
No. Standard blood panels — including complete blood counts and metabolic panels — do not measure the proteins associated with Alzheimer’s disease. They cannot detect amyloid plaques or tau tangles. Only specialized blood biomarker tests, ordered in specific clinical contexts, can provide that information.
Are the new Alzheimer’s blood tests available at my regular doctor’s office?
The Roche Elecsys pTau181, cleared by the FDA in October 2025, is specifically indicated for use in primary care settings. However, availability varies by location, practice, and insurance coverage. Not all primary care physicians are yet using it routinely. Ask your doctor whether it is an option for your situation.
If my blood biomarker test comes back positive, does that mean I have dementia?
Not definitively. A positive result indicates the presence of Alzheimer’s-related pathology — amyloid burden or tau accumulation — but diagnosis requires a complete clinical evaluation. Blood tests are used alongside other assessments, not as a standalone diagnostic tool.
How early can blood biomarker tests detect signs of Alzheimer’s?
Research has shown that blood biomarkers can detect signs of Alzheimer’s pathology up to 16 years before disease onset, according to a study of more than 2,000 older adults published in Nature Medicine. A separate study found a 10-year predictive window in independently living older adults.
Can a healthy person with no symptoms get a blood biomarker test to check their risk?
The FDA-cleared tests are approved for use in adults 50 and older who already have cognitive symptoms. They are not approved for general screening of healthy, asymptomatic individuals. Using them outside that context is not currently supported by clinical guidelines.
What proteins do the new blood tests actually measure?
The tests primarily measure phosphorylated tau proteins (p-tau217 and p-tau181), amyloid, and neurofilament light chain (NfL). These are proteins associated with the biological changes of Alzheimer’s disease, and their levels in the blood correlate with what is happening in the brain.
