Testing for dementia isn’t a single test. It’s a series of evaluations that typically begins with a doctor’s visit and may include cognitive screening, blood work, brain imaging, and sometimes a specialized neuropsychological assessment. The process works in layers: first ruling out treatable conditions that mimic dementia, then identifying whether cognitive decline is present, and finally determining what type of dementia may be causing it.
What Happens at the First Visit
A dementia evaluation usually starts with your primary care doctor reviewing your medical history, asking about your symptoms, and conducting a physical exam. Someone close to you, like a spouse or adult child, will often be asked to describe the changes they’ve noticed. This step matters more than people expect. You may not recognize the full extent of your own cognitive changes, and an outside perspective helps the doctor understand how daily functioning has shifted over time.
One structured way doctors gather this information is through a caregiver questionnaire. The AD8, for example, is a short interview given to someone who knows you well. It asks about changes in areas like judgment, interest in hobbies, and the ability to handle finances or remember appointments. A score of 2 or higher (out of 8) suggests cognitive impairment worth investigating further.
Cognitive Screening Tests
Short cognitive tests are one of the first tools used to measure how well your memory, attention, language, and reasoning are working. These are pencil-and-paper exercises administered in the doctor’s office, usually taking 10 to 30 minutes.
The two most widely used are the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). The MoCA is scored out of 30, and a score below 26 is generally considered the threshold for mild cognitive impairment. A score around 18 or lower may suggest Alzheimer’s disease, though no single standardized cutoff for dementia has been established. The MMSE is older and less sensitive to early or subtle decline, particularly the kind caused by problems with executive function (planning, organizing, multitasking) rather than memory alone. Both tests are influenced by age and education level, which doctors factor into their interpretation.
If you want to track your own cognition before or between doctor visits, the Self-Administered Gerocognitive Examination (SAGE) is a validated option you can take at home. Research from a Dutch memory clinic found that SAGE scores correlated well with standard neuropsychological tests. In earlier studies, it showed 95% sensitivity in distinguishing healthy adults from those with dementia, using a cutoff score of 16 or below. It’s not a replacement for a clinical evaluation, but it can flag changes worth bringing to your doctor.
Blood Tests and Lab Work
Before attributing cognitive symptoms to a degenerative brain disease, doctors need to rule out conditions that are treatable and sometimes fully reversible. A standard lab panel for a dementia workup includes thyroid function, vitamin B12 levels, a complete blood count, electrolytes, calcium, and blood sugar. An underactive thyroid or a B12 deficiency, for instance, can cause memory problems and confusion that look remarkably like dementia but resolve with treatment.
Depending on your history, additional tests may be ordered for things like syphilis, Lyme disease, HIV, liver function, or folic acid levels. Depression can also mimic or worsen cognitive decline, so a psychiatric evaluation is sometimes part of the workup.
A New Blood Test for Alzheimer’s
In a significant shift, the FDA has cleared the first blood test designed to help diagnose Alzheimer’s disease specifically. The test measures the ratio of two proteins in the blood that reflect the buildup of amyloid plaques in the brain, a hallmark of Alzheimer’s. In a clinical study of 499 cognitively impaired adults, 91.7% of those who tested positive were confirmed to have amyloid plaques by brain scan or spinal fluid testing. Among those who tested negative, 97.3% were confirmed negative by those same methods.
This test is currently intended for adults 55 and older who are already showing signs of cognitive decline, and it’s used in specialized care settings. It’s not a standalone diagnostic tool or a general screening test, but it can help doctors determine whether Alzheimer’s pathology is likely present without immediately jumping to more invasive or expensive procedures like a PET scan or spinal tap.
Brain Imaging
Imaging gives doctors a look at the brain’s structure and activity. The type of scan ordered depends on what question needs answering.
A structural MRI (or sometimes a CT scan) is typically the first imaging step. Its primary job is ruling out other causes of cognitive symptoms: tumors, strokes, bleeding, infections, or excess fluid buildup in the brain. In some cases, the specific pattern of brain shrinkage visible on MRI can also point toward a particular type of dementia.
PET scans go further. A type called FDG-PET measures how actively different brain regions are using glucose, which reflects how well neurons are functioning. This scan can detect dysfunction before structural changes become visible on MRI, making it useful for early diagnosis. It’s also particularly helpful for distinguishing Alzheimer’s from frontotemporal dementia, since each produces a distinct pattern of reduced brain activity in different regions.
Amyloid PET scans detect the protein deposits that define Alzheimer’s disease. These are highly sensitive and specific, but they’re expensive and not always necessary if other evidence already points clearly in one direction. The 2024 revised diagnostic criteria from the National Institute on Aging and the Alzheimer’s Association now define Alzheimer’s biologically, based on the presence of these protein markers, rather than solely on clinical symptoms. This framework increasingly allows blood-based biomarkers and PET imaging to work together in confirming a diagnosis.
The Neurological Exam
A neurological exam tests your movement, balance, reflexes, senses, and eye movements. These physical findings can reveal which type of dementia is involved. Gait and balance problems, for example, are strongly associated with Parkinson’s disease dementia. In one study, 93% of Parkinson’s patients with dementia had gait and balance disorders, compared to 43% of those without dementia. Rigidity, postural instability, facial masking (reduced facial expression), and speech changes are additional physical signs that help doctors distinguish between dementia types.
For vascular dementia, doctors look for evidence of stroke-related damage: weakness on one side of the body, abnormal reflexes, or visual field loss. These neurological findings, combined with imaging, help separate vascular causes from neurodegenerative ones.
Neuropsychological Testing
When screening tests raise concerns but the picture isn’t clear, a full neuropsychological evaluation provides the most detailed look at cognitive function. Administered by a neuropsychologist, this battery of tests takes several hours and measures memory, attention, processing speed, language, visuospatial skills, and executive function in much greater depth than an office screening can.
The results help in two ways. First, they establish a detailed cognitive profile that can distinguish between types of dementia. Alzheimer’s tends to hit memory hardest in the early stages, while frontotemporal dementia often affects personality and decision-making first. Second, they create a baseline. If testing is repeated a year or two later, the comparison reveals whether decline is progressing and how quickly.
How Long the Process Takes
There’s no fixed timeline. A straightforward case where screening, blood work, and imaging all point in the same direction might be wrapped up in a few weeks. More complex situations, especially when symptoms are mild or could have multiple causes, may involve referrals to a neurologist or memory clinic and take several months from the first appointment to a clear diagnosis. The process can feel slow, but each layer of testing narrows the possibilities and helps ensure the diagnosis is accurate, which directly affects what treatment options make sense going forward.