A blood test for Alzheimer's was cleared for use in May 2025. It answers a different question from a memory test, and knowing which is which matters.
In May 2025 the Food and Drug Administration cleared the first blood test for Alzheimer's disease. It is a real milestone. It is also narrower than the headlines suggested, and it answers a different question from the one most people are asking when they worry about their memory.
What Does the Test Actually Measure?
It measures two proteins in a blood sample and reports the ratio between them. That ratio tracks whether amyloid plaques are building up in the brain. Amyloid is one of the changes associated with Alzheimer's disease, and until now the only ways to see it were a brain scan or a spinal tap.
In the studies behind the clearance, the test agreed with spinal fluid results about 92% of the time when plaques were present, and about 97% of the time when they were not.
Why Does a Blood Test Not Replace a Memory Test?
Because they answer different questions.
A blood test tells you what is accumulating in your brain. A memory test tells you how well you are actually remembering things. Those are not the same, and the second one is what you live with day to day.
Plenty of people have amyloid in their brains and no trouble with memory. Plenty of people have memory trouble that has nothing to do with amyloid, including causes that can be treated. Neither test is a substitute for the other, and neither one is a diagnosis on its own.
Who Can Get One Right Now?
The clearance covers adults aged 55 and older who already have signs or symptoms of Alzheimer's disease, and it is meant to be used by doctors who specialize in memory disorders. It is not a screening test for people who feel fine, and it is not something you can decide to have on your own.
If your memory is a concern, the first step is still a conversation with your doctor, who decides whether a test like this would tell them anything useful.
What Can You Do If You Are Worried Now?
Start with something you can measure and repeat. A memory test gives you a baseline, and a baseline is what turns a vague worry into something you and your doctor can actually track.
See what the Memory Exam measures, or compare the options available to you.
Where This Information Comes From
Food and Drug Administration clearance of the Lumipulse G pTau217 and beta-Amyloid 1-42 plasma ratio test, May 2025.