Two kinds of blood work
When people ask about blood tests for memory loss, they usually mean one of two things. The first is the routine lab work every memory evaluation should include, which looks for treatable causes of memory problems. The second is a newer group of tests that look for signs of Alzheimer's disease itself.
Routine lab work
Your doctor will typically check:
- Vitamin B12, because a deficiency can cause memory and thinking problems that improve with treatment
- Thyroid function (TSH), because an underactive thyroid can slow thinking
- A complete blood count and metabolic panel, which screen for anemia, infection, kidney and liver problems, blood sugar, and sodium levels
- Other tests when your history calls for them, such as folate or tests for certain infections
These tests rule out other causes of memory problems, and some of what they find is fully treatable. Our guide to treatable causes of memory loss explains more.
Alzheimer's blood tests
Newer blood tests measure proteins linked to the brain changes of Alzheimer's disease, most often a form of tau protein called p-tau217, sometimes combined with a measure of amyloid. In May 2025 the FDA cleared the first of these tests, Fujirebio's Lumipulse pTau217/β-amyloid 1-42 plasma ratio. Roche's Elecsys pTau181 followed in October 2025 for use in primary care, where a negative result helps rule out Alzheimer's as the cause of symptoms. In August 2026 the FDA cleared two more: C2N Diagnostics' PrecivityAD2, the first cleared for adults as young as 40, and Roche's Elecsys pTau217, which can help rule Alzheimer's in or out in both primary and specialty care. All four are for adults with signs or symptoms of cognitive decline, and a clinician orders them. Commercial laboratories also offer their own versions.
A blood draw can now help a doctor judge whether memory symptoms are likely due to Alzheimer's and whether a patient should move on to confirmatory testing. That makes the path to a diagnosis faster and less invasive for many families.
Who the tests are for
Today's Alzheimer's blood tests are for people who already have memory or thinking symptoms, ordered and interpreted by a clinician as part of a full evaluation. The Alzheimer's Association's 2025 clinical practice guideline recommends them for people with cognitive impairment who are being evaluated in specialty memory care.
For people without symptoms, experts advise against these tests outside of research studies. A positive result in someone with no symptoms is harder to interpret, and no FDA-approved treatment exists yet for people who have amyloid but no symptoms. If you see an Alzheimer's blood test offered online or as part of a wellness package, talk with a doctor first about what you would do with the answer.
How blood tests fit with other testing
A blood test is one piece of the picture. A diagnosis also draws on your history, what your family has noticed, cognitive testing, and often an MRI. Before anyone starts Leqembi or Kisunla, the care team must confirm amyloid in the brain, using an amyloid PET scan, a spinal fluid test, or in some cases a highly accurate blood test.
Questions to ask your doctor
- Which routine labs have I had, and were any results out of range?
- Would an Alzheimer's blood test help in my situation, and which one would you order?
- What would we do differently depending on the result?
- Will Medicare or my insurance cover the test?
- If the result is positive, what are the next steps?
This guide is for education and is not medical advice. Treatment decisions are made with your provider after a full evaluation.