For many years, the only ways to see Alzheimer's changes in a living person were a costly brain scan or a spinal tap. Now there are blood tests that can help. A nurse draws blood from your arm, and a lab looks for proteins linked to Alzheimer's.¹

These tests are a big step, but they are not a simple "yes or no" for Alzheimer's. They are made for people who already have memory or thinking problems, and the doctor reads the result along with other tests.^1,9 This page explains what is cleared as of October 2026, who should get a test, how accurate the tests are, and what they may cost.

Key points

As of October 2026, the FDA has cleared four Alzheimer's blood tests: Lumipulse (May 2025), Elecsys pTau181 (October 2025), and PrecivityAD2 and Elecsys pTau217 (August 2026).^1,3,5,7
The tests look for signs of amyloid (a sticky protein that builds up between brain cells in Alzheimer's).¹
They are for adults with symptoms such as memory loss, after a full check-up. They are not screening tests for people who feel fine.^8,9
A negative result is usually reliable. A positive result often needs more testing or a careful look by a specialist.^1,2
Medicare Part B usually pays for lab tests a doctor orders when they are medically needed. Ask about your own costs before the blood draw.¹⁰

What do these blood tests look for?

Alzheimer's disease causes two main changes in the brain. Amyloid clumps into plaques between brain cells. Tau (a protein inside brain cells) twists into tangles. Read more on Alzheimer's disease.

Tiny amounts of these proteins leak into the blood. The new tests measure them. The most useful marker so far is a form of tau called pTau217 ("p-tau two-seventeen"). The "p" means a small chemical tag is attached. Another form is called pTau181.^1,2,4

Some tests measure one protein. Others compare two proteins as a ratio (one number divided by another). For example, the Lumipulse test compares pTau217 with a type of amyloid called beta-amyloid 42. The ratio tracks well with whether plaques are present in the brain.¹

Until now, doctors confirmed amyloid with an amyloid PET scan or a spinal fluid test. PET scans cost a lot, take time and use radiation. A spinal tap uses a needle in the lower back.¹ A blood test may help some people skip those tests, or help the doctor decide who needs them.^2,8

Which tests has the FDA cleared?

"Cleared" means the FDA reviewed the test and allowed it to be sold for a specific use. Each test has its own rules about who it is for.

Test (maker)	When cleared	Who it is for	What it measures
Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio (Fujirebio)	May 2025	Adults 55 and older with signs of memory or thinking decline, seen in a specialty clinic	Ratio of pTau217 to amyloid 42
Elecsys pTau181 (Roche)	October 2025	Adults 55 and older with memory or thinking complaints, in primary care. Used to rule out amyloid	pTau181 alone
PrecivityAD2 (C2N Diagnostics)	August 2026	Adults 40 and older with signs of memory or thinking problems, with a clinician skilled in memory care	Two amyloid proteins and two tau forms, combined into one score
Elecsys pTau217 (Roche)	August 2026	Adults 55 and older with signs of decline linked to Alzheimer's, in primary or specialty care	pTau217 alone

Sources for the table: FDA and Alzheimer's Association announcements.^{1,2,3,4,5,6,7}

The first test, Lumipulse, was cleared on May 16, 2025.¹ The Elecsys pTau181 test followed in October 2025. It was the first blood test cleared for primary care, where most people first bring up memory worries.³ In August 2026, the FDA cleared two more within days of each other. PrecivityAD2 is the first cleared for adults as young as 40.^5,7 Elecsys pTau217 can be used to rule amyloid in or out, in both primary and specialty care.⁵

More tests may be cleared soon. Ask your doctor which test your clinic uses and why.

Who should get a blood test?

A blood test may make sense if all of these are true:

You (or your family member) have new problems with memory or thinking that a doctor has noticed or confirmed.
A doctor has done a full check-up first. This includes your health history, a physical exam, memory and thinking tests, and checks for other causes.
The result would help answer a real question, such as "Is this likely Alzheimer's?" or "Should we look into the new anti-amyloid treatments?"

The Alzheimer's Association's first guideline on these tests came out in July 2025. It says doctors should not order a blood test before a full clinical evaluation. It also says doctors should think about how likely Alzheimer's is for that person before they read the result.⁸

Memory problems have many causes. Some can be treated, such as low vitamin B12, thyroid problems, medicine side effects, depression or sleep apnea. See treatable conditions that look like dementia. A blood test for Alzheimer's does not check for these. That is why the full check-up comes first.

Your first step is usually a visit with your regular doctor. See the first doctor visit about memory and which specialist to see.

Not for people without symptoms

These tests are not meant to screen people who have no memory or thinking problems.^1,9 Every FDA-cleared use is for people who already have signs or symptoms.^1,2,4,6

There are good reasons for this. Amyloid can build up in the brain for years before any symptoms appear.¹ Researchers are still studying what an early result means and how it affects people to learn it.⁹

The new anti-amyloid medicines are approved only for people who already have symptoms. See lecanemab and donanemab. If you feel well but are worried about your risk, talk with your doctor. You might also look into joining a clinical trial. Some trials test people without symptoms as part of the study.

How accurate are the tests?

Accuracy is usually checked by comparing the blood test with an amyloid PET scan or spinal fluid test in the same people. Here is what the FDA reviews found, in plain numbers.

Lumipulse (specialty clinics). In a study of 499 adults with memory problems:¹

When the test was positive, about 92% had amyloid confirmed by PET or spinal fluid. That is about 11 in 12 people.
When the test was negative, about 97% truly had no amyloid. That is about 36 in 37 people.
Fewer than 1 in 5 people got an "in-between" (indeterminate) result that did not answer the question.

Elecsys pTau181 (primary care, rule-out test). In a study of 312 people similar to primary care patients:²

When the test was negative, about 98% had a negative amyloid PET scan. That is about 49 in 50 people.
When the test was positive, only about 22% had amyloid on PET. That is about 1 in 5.
So a negative result is the useful one. A positive result does not mean Alzheimer's. It means the doctor should look further.

Elecsys pTau217 (primary and specialty care). In a study of 958 people:⁴

When the test was positive, about 89% had amyloid on PET. That is about 9 in 10.
When the test was negative, about 95% had no amyloid. That is about 19 in 20.
About 1 in 5 people (20%) got an "intermediate" result. These people need more testing.
The FDA notes that positive results will be right less often in primary care, where fewer patients have amyloid.⁴

PrecivityAD2. This test gives a score from 0 to 100. The result is reported as positive, likely positive, or negative. A negative result means the doctor should look for other causes of the symptoms. A positive result is consistent with amyloid, but it does not prove Alzheimer's by itself.⁶

The guideline's accuracy bar

The 2025 Alzheimer's Association guideline set two levels for tests used in memory clinics:⁸

A triage test should catch at least 90% of people with amyloid and correctly clear at least 75% of people without it. A negative result can rule out Alzheimer's changes. A positive result should be confirmed with a PET scan or spinal fluid test.
A confirmatory test should reach at least 90% on both measures. It can take the place of a PET scan or spinal fluid test.

The guideline panel found that accuracy varies a lot between tests, and many tests sold in the U.S. do not meet these levels.⁸ The panel did not name specific brands.⁸ Ask your doctor whether the test you are offered is FDA-cleared and how accurate it is.

What could affect the result?

Blood tests can be thrown off by things other than Alzheimer's.

Kidney disease. When the kidneys do not work well, levels of pTau217 and pTau181 in the blood can rise. Some ratio tests are less affected.¹¹ One FDA review noted that people with chronic kidney disease were left out of a study that set normal ranges for this reason.² Tell the doctor if you have kidney disease.
Lab handling. How the blood sample is collected, stored and frozen matters. The labs must follow strict steps.^4,6
Age and other illnesses. Some people have amyloid without it being the main cause of their memory problems. Older adults often have more than one brain condition at once, such as Alzheimer's plus small strokes. See mixed dementia.

This is why the FDA says each result must be read together with other information about the person.^1,4

Understanding your result

If the result is negative

Amyloid is unlikely to be the cause of the symptoms.^1,2
The doctor should look for other causes, such as other dementia types, medicines, mood or sleep problems.^2,6
Keep up regular checkups. Tell the doctor if symptoms change.

If the result is positive

Amyloid is likely present, but this alone does not diagnose Alzheimer's.^4,6
With some tests, especially the pTau181 rule-out test, a positive result needs more testing.²
The doctor may order a PET scan or spinal fluid test, or refer you to a specialist.

An "in-between" result is common, about 1 in 5 for some tests.^1,4 It is not a failure. It just means the test could not decide, and other tests are needed.

A positive result can be hard to hear. It may help to bring a family member or friend to the visit where you get results. If you feel hopeless or have thoughts of suicide, call or text 988 any time. If someone is in danger, call 911. Our page on the first 30 days after a diagnosis has next steps.

What do the tests cost?

Prices and coverage change often. These facts are current as of October 2026.

Medicare. Original Medicare Part B covers clinical lab tests, including blood tests, when they are medically needed, a doctor orders them, and a Medicare-approved lab does the test. You usually pay nothing for these covered tests.¹⁰
Screening is different. These blood tests are cleared only for people with symptoms.^1,9 A test ordered just to check someone with no symptoms may not count as medically needed.
Medicare Advantage and private insurance. Coverage varies by plan and by test. Call your plan and ask.
Paying yourself. Prices vary by lab. Ask for the price in writing before the blood draw.

Amyloid PET scans are costly, which is one reason blood tests matter.¹ For PET scan coverage, see brain scans. If a blood test leads to treatment, see paying for new Alzheimer's drugs.

Before the test, ask: "Is this test FDA-cleared? Does Medicare or my plan cover it here? What will I owe?" Write down the answers in a memory notebook.

Questions to ask the doctor

Before the test

Why do you think a blood test would help in my case?
Which test will you use? Is it FDA-cleared for someone my age and in this setting?
Have you checked for other causes of my memory problems first?
Do I have kidney disease or anything else that could affect the result?

About the result

What does my result mean for me? Was it positive, negative or in-between?
Do I need a PET scan, spinal fluid test or a specialist visit next?
Does this change whether I could get an anti-amyloid treatment?

About cost and support

Will Medicare or my plan pay for this test at this lab?
Who can I call with questions after I get the result?

The Alzheimer's Association 24/7 Helpline at 800-272-3900 can answer questions about testing and help you find doctors.⁵

Sources

U.S. Food and Drug Administration. FDA clears first blood test used in diagnosing Alzheimer's disease. FDA, 2025. FDA
U.S. Food and Drug Administration. 510(k) decision summary K252163: Elecsys Phospho-Tau (181P) Plasma. FDA, 2025. FDA
Alzheimer's Association. Alzheimer's Association welcomes FDA clearance of first blood test for use in primary care to rule out Alzheimer's-related amyloid pathology. Alzheimer's Association, 2025. alz.org
U.S. Food and Drug Administration. 510(k) decision summary K261686: Elecsys Phospho-Tau (217P) Plasma. FDA, 2026. FDA
Alzheimer's Association. FDA clears Elecsys pTau217 blood test for Alzheimer's. Alzheimer's Association, 2026. alz.org
U.S. Food and Drug Administration. 510(k) summary K253240: PrecivityAD2 Test. FDA, 2026. FDA
Alzheimer's Association. Alzheimer's Association statement on FDA clearance of PrecivityAD2 blood test. Alzheimer's Association, 2026. alz.org
Alzheimer's Association. New clinical practice guideline for blood-based biomarkers (AAIC 2025 news release). Alzheimer's Association, 2025. alz.org
Alzheimer's Association. Earlier diagnosis. Alzheimer's Association, 2026. alz.org
Medicare.gov. Clinical laboratory tests. Centers for Medicare & Medicaid Services, 2026. Medicare.gov
Janelidze S, et al. Mitigating the associations of kidney dysfunction with blood biomarkers of Alzheimer disease by using phosphorylated tau to total tau ratios. JAMA Neurol, 2023. PMC

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.