Happy & Healthy with Amy

Alzheimer's Blood Biomarker Test: What It Can and Can't Tell You

• Amy Lang

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0:00 | 41:53

What if a simple blood test could help doctors determine whether Alzheimer's is behind your mom's memory problems?

It sounds almost too good to be true. But Alzheimer's blood tests are changing how doctors evaluate cognitive decline. And depending on which test is used, the results can be remarkably accurate.

But, keep in mind, not all blood tests are equally reliable. And even a positive result doesn't necessarily mean Alzheimer's is causing someone's memory and thinking problems.

In this episode of Happy & Healthy with Amy, I'm breaking down how Alzheimer's blood tests work, what they measure, and how they compare with amyloid PET scans and spinal fluid tests.

You'll also learn why one blood test may be enough for some patients but not others, who should consider biomarker testing, and what questions to ask your doctor to get a more accurate diagnosis.

Because the goal isn't simply to find evidence of Alzheimer's in the brain. It's to understand what's actually causing the symptoms.

Free Resource

đź“Ą  Download Alzheimer's Diagnosis Checklist


What to Listen For

  • 0:00 —  Can a Simple Blood Test Detect Alzheimer's?
  • 00:35 — MCI isn't Alzheimer's. Why a diagnosis of mild cognitive impairment doesn't explain what's actually causing the memory problems—and why finding the cause matters.
  • 01:34 — Could your parent's diagnosis change? How amyloid biomarker results led specialists to change more than one-third of uncertain diagnoses in one study.
  • 04:06 — Amyloid vs. tau: What's happening in the brain? Learn the difference between plaques and tangles, and why those two proteins are central to Alzheimer's testing.
  • 07:33 — What an amyloid PET scan can—and can't—tell you. Why seeing plaques doesn't necessarily mean someone has advanced Alzheimer's or explain all of their symptoms.
  • 12:38 — Why less amyloid in spinal fluid can mean more plaque in the brain. Amy breaks down the surprisingly simple logic behind the Aβ42/Aβ40 ratio.
  • 16:13 — The Alzheimer's blood test breakthrough. What changed with the first FDA-cleared Alzheimer's blood test in May 2025—and why it isn't intended for everyone.
  • 17:46 — What p-tau217 actually measures. Amy's coffee shop umbrella analogy explains why a tau blood test can provide evidence of amyloid buildup without measuring plaques directly.
  • 23:42 — When is one blood test enough? Discover the difference between a triage test and a confirmatory test—and why some results still require a PET scan or spinal tap.
  • 26:28 — Blood test, PET scan, or spinal tap: Which is best? Why the right choice depends on the person, the specific test, and the clinical circumstances.
  • 34:45 — What to ask your doctor before accepting a diagnosis. The questions that can help you understand whether Alzheimer's pathology has been confirmed, how reliable the evidence is, and whether additional testing could help.

Alzheimer's blood tests are an important breakthrough, but getting an accurate diagnosis means looking beyond any single test result. Understanding what a test measures, how reliable it is, and whether it fits the person's symptoms can help you make more informed decisions.

Listen to this episode, download my free Alzheimer's Diagnosis Checklist to prepare for your next doctor's appointment, and follow Happy & Healthy with Amy on Spotify or Apple Podcasts. And if someone you love is navigating memory problems right now, please share this episode with them—because knowing which questions to ask can make all the difference.

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