Checking for dementia involves a layered process that typically starts with cognitive screening tests in a doctor’s office and may expand to brain imaging, blood work, and functional assessments. There is no single test that confirms dementia. Instead, clinicians piece together results from several evaluations to determine whether cognitive decline is present, how severe it is, and what’s causing it. The average time from first symptoms to a formal diagnosis is about 3.4 years, partly because symptoms develop gradually and partly because many treatable conditions can look like dementia and need to be ruled out first.
What Doctors Look for First
A dementia evaluation usually begins with your primary care doctor asking detailed questions about the changes you or your family have noticed. They’ll want to know which cognitive abilities have shifted: memory, language, problem-solving, attention, social behavior, or the ability to navigate familiar places. Under current diagnostic standards, memory loss alone is not required for a diagnosis. Impairment in just one cognitive area can qualify, though Alzheimer’s disease specifically still requires decline in at least two areas, one of which must be memory.
Your doctor will also review your full medication list, medical history, and any recent life changes. This matters because dozens of conditions can mimic dementia, and identifying those early can save years of unnecessary worry.
Cognitive Screening Tests
The most common in-office screening tools are the Montreal Cognitive Assessment (MoCA) and the Mini-Mental State Examination (MMSE). Both take around 10 to 15 minutes. You’ll be asked to remember a short list of words, draw a clock face, copy a geometric shape, count backward, name animals, and follow multi-step instructions. These tasks test memory, attention, language, and visual-spatial skills all at once.
The MoCA is scored out of 30 points. A score below 26 is generally considered the threshold for mild cognitive impairment, though a standard cutoff for dementia itself hasn’t been formally established. A score around 18 is sometimes used as a reference point for Alzheimer’s disease. The MMSE is also scored out of 30, but studies have used varying threshold scores, which makes direct comparisons tricky. Neither test is definitive on its own. A low score signals the need for deeper evaluation, while a normal score in someone with clear functional decline doesn’t rule dementia out.
Ruling Out Treatable Conditions
Before diagnosing dementia, doctors need to eliminate a long list of medical problems that can impair thinking but respond to treatment. This is one of the most important parts of the process, because some of these conditions are fully reversible.
- Thyroid disorders: Both overactive and underactive thyroid function interfere with cognition. A simple blood test can detect this.
- Vitamin deficiencies: Low B12 and other nutritional deficiencies can cause confusion, memory problems, and even personality changes.
- Infections: Lyme disease, syphilis, HIV, and urinary tract infections (especially in older adults) can all produce dementia-like symptoms.
- Medication side effects: Certain drugs, particularly sedatives, anticholinergics, and some pain medications, can dull thinking significantly.
- Depression: Severe depression in older adults sometimes causes concentration and memory problems so pronounced it’s been called “pseudodementia.”
- Normal pressure hydrocephalus: A buildup of fluid in the brain’s cavities that causes cognitive problems, difficulty walking, and loss of bladder control. It can often be treated with a surgical shunt.
- Subdural hematoma: A collection of blood inside the skull after a fall or head injury, sometimes one that seemed minor at the time.
- Liver or kidney disease: Both can allow toxic waste products to accumulate in the blood, clouding mental function.
- Heart and lung conditions: Anything reducing oxygen delivery to the brain can impair cognition.
Even uncorrected vision or hearing loss can create symptoms that look like cognitive impairment. Standard blood panels checking thyroid function, B12 levels, blood sugar, and liver and kidney markers are a routine part of any dementia workup.
The Neurological Exam
A neurologist will perform a physical exam focused on how well your nervous system is functioning. This includes testing muscle strength and coordination by having you move your arms and legs, checking fine motor skills like writing your name, and evaluating your gait by asking you to walk a straight line or take steps on your heels and toes. Reflexes are tested with the familiar rubber hammer tap to the knee, and the soles of your feet may be stimulated to check nerve responses.
These tests aren’t measuring memory. They’re looking for signs of stroke, Parkinson’s disease, tumors, or other neurological conditions that could explain the symptoms or point toward a specific type of dementia.
Brain Imaging
Most dementia evaluations include at least one brain scan. An MRI provides detailed structural images and can reveal patterns of brain shrinkage specific to different types of dementia. In Alzheimer’s disease, the hippocampus (the brain’s memory center) and the temporal and parietal lobes show significant shrinkage, while areas controlling basic movement and sensation are relatively preserved. In vascular dementia, the scan instead shows damage to the brain’s white matter, small strokes, and enlarged spaces around blood vessels.
PET scans go a step further by measuring how actively different brain regions are using energy. Alzheimer’s disease produces a distinctive pattern where energy use drops first in areas deep in the middle of the brain, then spreads to the temporal and parietal lobes, and eventually reaches the frontal lobes. Vascular dementia shows reduced energy use in areas corresponding to blood vessel damage and stroke rather than following this specific progression. These imaging patterns help clinicians distinguish between dementia types when symptoms alone aren’t enough.
Blood Tests and Biomarkers
A major recent advance is a blood test that can detect Alzheimer’s-related brain changes. In early 2025, the FDA cleared the first blood test for use in diagnosing Alzheimer’s disease. It measures the ratio of two proteins linked to amyloid plaques, the hallmark deposits found in Alzheimer’s brains. In a clinical study of 499 patients with cognitive symptoms, 91.7% of those who tested positive were confirmed to have amyloid plaques by PET scan or spinal fluid testing. Among those who tested negative, 97.3% were confirmed negative by those same methods.
The test isn’t perfect. Fewer than 20% of patients received an indeterminate result, meaning the test couldn’t clearly classify them. It’s also intended for people already showing signs of cognitive decline in a specialist setting, not as a general screening tool for people without symptoms. Still, it represents a significant shift from the previous standard, which required either an expensive PET scan or a spinal tap to detect amyloid pathology.
Spinal fluid testing remains an option, particularly at specialized memory clinics. It measures levels of amyloid and tau proteins directly. An abnormal ratio between these two proteins helps separate Alzheimer’s from other causes of dementia.
Genetic Testing
The APOE gene test identifies whether you carry a variant called APOE-e4, which increases the risk of developing Alzheimer’s disease. An estimated 15% to 25% of people carry one copy of this gene, and 2% to 5% carry two copies. Having the gene raises your risk but does not mean you will develop Alzheimer’s. Many carriers never do, and many people who develop the disease don’t carry it.
This test is voluntary and is most often considered by people with a strong family history of Alzheimer’s. It can also help guide treatment decisions for someone who already has a diagnosis. It’s a risk assessment tool, not a diagnostic one.
How Daily Functioning Factors In
Cognitive test scores and brain scans tell only part of the story. A key part of any dementia evaluation is assessing how well a person manages everyday tasks. Clinicians look at two categories of daily activities. Basic activities include bathing, grooming, getting dressed, using the toilet, and feeding yourself. Instrumental activities are more complex: managing finances, cooking meals, doing laundry, taking medications on schedule, driving, and using a phone.
Someone with mild cognitive impairment might struggle with instrumental tasks like paying bills or following a recipe but handle all basic self-care without help. As dementia progresses, basic activities become difficult too. This functional assessment helps determine not just whether dementia is present but how far it has advanced, which directly shapes care planning.
What the Process Looks Like in Practice
A typical evaluation unfolds over several appointments. The first visit often involves the cognitive screening, a medical history review, and blood work to check for reversible causes. If results suggest further investigation, you’ll be referred to a neurologist or a memory clinic for brain imaging, a full neurological exam, and possibly biomarker testing. Some academic medical centers can complete the entire workup in one or two intensive visits, while community settings may spread it over weeks or months.
Family members or close friends are often asked to attend at least one appointment. They can provide observations about changes that the person being evaluated may not recognize in themselves, which is critical information for the clinician. If you’re concerned about a loved one, keeping a written log of specific incidents (getting lost on a familiar route, repeating the same question within minutes, difficulty managing medications) gives the doctor concrete examples to work with rather than vague concerns.