Getting tested for Alzheimer’s typically starts with a visit to your primary care doctor, who will run a series of evaluations to assess your memory, rule out other causes of cognitive decline, and decide whether you need specialist referral. There isn’t a single test that confirms Alzheimer’s on its own. Instead, diagnosis relies on a combination of cognitive screening, blood work, brain imaging, and in some cases newer biomarker tests that detect the disease’s signature proteins.
Start With Your Primary Care Doctor
The first step is scheduling an appointment with your regular doctor and being specific about what you’ve noticed. Bring a close family member or friend who can describe changes they’ve observed in your memory, behavior, or daily functioning. Doctors rely heavily on this outside perspective because people experiencing cognitive decline often underestimate or don’t notice their own symptoms.
Your doctor will review your full medical history, current medications (some can cause memory problems as a side effect), and any family history of dementia. They’ll also order standard blood tests to check for conditions that can mimic Alzheimer’s. The American Academy of Neurology recommends screening for thyroid dysfunction, vitamin B12 deficiency, and folate deficiency during any cognitive evaluation. These are cheap, routine blood draws, and if one of them turns up abnormal, treating it may improve or even reverse your cognitive symptoms without any further workup.
What Cognitive Screening Looks Like
During your visit, you’ll take a short pen-and-paper test that measures memory, attention, language, and reasoning. The two most common are the Mini-Mental State Exam (MMSE) and the Montreal Cognitive Assessment (MoCA). Both are scored out of 30 and take roughly 10 to 15 minutes.
On the MMSE, a score of 24 or above is considered normal. On the MoCA, the normal cutoff is 26, with an extra point added if you have fewer than 12 years of formal education. The MoCA is generally better at catching early or subtle cognitive changes. In head-to-head comparisons, it distinguished between people with no symptoms and those with early-stage decline, while the MMSE often missed those differences. If your score falls below the cutoff, that doesn’t mean you have Alzheimer’s, but it does signal the need for deeper evaluation.
Some doctors also use more detailed neuropsychological testing, which can take several hours and is usually administered by a specialist. These longer batteries break down your performance across specific areas like word recall, spatial reasoning, and processing speed, helping to pinpoint exactly which cognitive functions are affected and how severely.
The New Blood Test for Alzheimer’s
In 2025, the FDA cleared the first blood test specifically designed to help diagnose Alzheimer’s disease. Made by Fujirebio, the test measures two proteins in your blood: p-tau 217 and beta-amyloid 1-42. The ratio between these two proteins indicates whether amyloid plaques, one of Alzheimer’s hallmark features, have built up in your brain.
In a clinical study of 499 people with cognitive impairment, 91.7% of those who tested positive on the blood test were confirmed to have amyloid plaques by PET scan or spinal fluid analysis. Among those who tested negative, 97.3% were confirmed negative by those same methods. That’s a high degree of accuracy for a simple blood draw. However, up to 20% of patients received an indeterminate result, meaning the test couldn’t clearly classify them one way or the other.
This test is designed for adults 55 and older who are already showing signs of cognitive decline. It’s not a screening tool for people with no symptoms, and it’s not a standalone diagnosis. Your doctor would use the result alongside cognitive testing and imaging to build a complete picture. Availability is still expanding, so not every clinic offers it yet.
Brain Imaging: MRI and PET Scans
Most people undergoing an Alzheimer’s workup will get a structural brain scan, usually an MRI. This shows whether there’s been shrinkage in brain regions associated with Alzheimer’s, and it also helps rule out other causes of cognitive decline like strokes, tumors, or fluid buildup.
If your doctor needs more definitive evidence, they may order a PET scan. Two types are relevant to Alzheimer’s:
- Amyloid PET detects beta-amyloid plaques, one of the earliest biological changes in Alzheimer’s. A negative scan means few or no plaques are present, which makes Alzheimer’s much less likely. A positive scan confirms plaques are there but doesn’t necessarily mean they’re causing your symptoms.
- Tau PET detects neurofibrillary tangles, the other protein hallmark of Alzheimer’s. Unlike amyloid PET, which gives a yes-or-no answer, tau PET shows where tangles are located and how far they’ve spread. A positive tau PET increases confidence that Alzheimer’s is actively driving cognitive decline, while being amyloid-positive but tau-negative suggests something else may be the primary cause of symptoms.
Under the 2024 diagnostic framework from the Alzheimer’s Association, the disease is now defined biologically rather than purely by symptoms. Amyloid PET is considered a “Core 1” biomarker for establishing whether Alzheimer’s pathology is present, while tau PET is a “Core 2” biomarker that helps stage how far the disease has progressed.
Insurance Coverage for PET Scans
Medicare historically restricted coverage for amyloid PET scans to clinical research studies. That changed in October 2023, when the Centers for Medicare and Medicaid Services ended that restriction and allowed regional Medicare contractors to make their own coverage decisions. This means coverage now varies by region. If your doctor recommends a PET scan, check with your specific Medicare plan or private insurer before scheduling. Out-of-pocket costs for amyloid PET can run several thousand dollars without coverage.
Spinal Fluid Analysis
A lumbar puncture (spinal tap) can measure the same proteins that accumulate in the brains of people with Alzheimer’s. In cerebrospinal fluid, low levels of beta-amyloid 42 and elevated levels of tau proteins are established markers of the disease. The procedure involves inserting a needle into the lower back to collect a small sample of fluid. It takes about 30 minutes, and most people experience mild soreness or a headache afterward that resolves within a day or two.
Spinal fluid testing has been used for years in research and specialty clinics, particularly when PET scans aren’t available or when results from other tests are inconclusive. With the arrival of accurate blood tests, spinal taps may become less common in routine diagnostic workups, but they remain a reliable option.
Genetic Testing and What It Can Tell You
You may have heard about the APOE-e4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s. Carrying one copy of this gene variant increases your risk, and carrying two copies increases it substantially. But having the gene doesn’t mean you’ll develop Alzheimer’s, and many people with Alzheimer’s don’t carry it at all.
Current practice guidelines do not recommend routine APOE testing as part of a diagnostic workup. The gene doesn’t provide definitive diagnostic information. One important exception: if you’re being considered for one of the newer anti-amyloid therapies like lecanemab, APOE genotyping is recommended before starting treatment because carriers, especially those with two copies, face a higher risk of brain swelling and bleeding as a side effect. Any genetic testing should be preceded by genetic counseling so you understand what the results do and don’t mean.
What Happens After Testing
Your doctor will piece together results from cognitive tests, blood work, imaging, and any biomarker tests to reach a diagnosis. In many cases, a primary care doctor will refer you to a neurologist or a memory clinic for this final stage, especially if results are mixed or if you’re in the early stages where the picture is less clear.
A diagnosis might come back as mild cognitive impairment (a stage of noticeable decline that doesn’t yet interfere significantly with daily life), Alzheimer’s disease at a specific stage, or a different form of dementia entirely. The process from first appointment to final diagnosis can take weeks to a few months, depending on how many tests are needed and how quickly you can get specialist appointments. Bringing organized notes about your symptoms, their timeline, and your family medical history to every appointment helps move things along.