Yes, there are several types of tests used to diagnose dementia, ranging from simple pen-and-paper cognitive screenings to advanced brain scans and blood tests. No single test confirms dementia on its own. Instead, doctors use a combination of cognitive assessments, lab work, and sometimes imaging to build a complete picture of what’s causing memory or thinking problems.
How the Diagnostic Process Typically Works
Most people start with their primary care doctor. At that first visit, the doctor will ask about your symptoms, how they affect daily life (cooking, paying bills, personal care), and whether anyone in your family has had dementia. They’ll do a physical exam and order routine blood and urine tests. These aren’t looking for dementia directly. They’re ruling out treatable conditions that can mimic it, like thyroid problems or vitamin B12 deficiency.
If those come back normal and cognitive concerns remain, the next step is a referral to a specialist: a neurologist, geriatrician, or psychiatrist who focuses on older adults. The specialist will run more detailed memory tests and may order brain imaging. The whole process can take weeks to months depending on wait times and how many tests are needed. Research from the Alzheimer’s Society found that 1 in 4 people wait two years before even seeking help for their symptoms, so the diagnostic timeline often depends more on when someone first brings up concerns than on the testing itself.
Cognitive Screening Tests
Cognitive screening is usually the first formal step. These are short, structured tests that measure memory, language, problem-solving, and orientation (knowing the date, time, and where you are). Two of the most common are the Montreal Cognitive Assessment (MoCA) and the Mini-Mental State Examination (MMSE). On the MoCA, a score below 26 out of 30 is the standard threshold that raises concern for mild cognitive impairment, though there’s no single agreed-upon cutoff for dementia itself. The MMSE works similarly but uses varying threshold scores depending on the clinical setting.
These tests take about 10 to 15 minutes and are given in a doctor’s office. They’re useful for flagging problems, but a low score doesn’t automatically mean dementia. Factors like anxiety, poor sleep, depression, and even hearing loss can drag scores down. That’s why screening results are always interpreted alongside everything else the doctor knows about you.
At-Home Screening With the SAGE Test
If you want to check for early signs before seeing a doctor, the Self-Administered Gerocognitive Examination (SAGE) is a free test developed by researchers at Ohio State University. You can print it out and take it at home with a pen. It evaluates six areas: memory, reasoning, language, executive function (planning and organizing), orientation, and visuospatial ability (judging where objects are in space and how they relate to each other).
SAGE is not a diagnostic test. It’s a screening tool that can help you and your doctor decide whether further evaluation makes sense. If you take it and your results concern you, bring the completed test to your next appointment.
Blood Tests That Rule Out Other Causes
Some conditions cause memory loss and confusion that look like dementia but are entirely reversible. Doctors routinely test for these before pursuing a dementia diagnosis. The most important blood tests check thyroid function and vitamin B12 levels. An underactive thyroid slows thinking and causes fatigue that can be mistaken for cognitive decline. Vitamin B12 deficiency does something similar, and studies using sensitive markers of B12 status (methylmalonic acid and holotranscobalamin) have found consistent links between low B12 and increased risk of cognitive decline and dementia diagnosis. If either condition is the culprit, treatment can improve or fully resolve symptoms.
Other blood work may check for infections, liver or kidney problems, diabetes, and electrolyte imbalances, all of which can affect cognition.
The New Blood Test for Alzheimer’s
In early 2025, the FDA cleared the first blood test specifically designed to help diagnose Alzheimer’s disease. Called the Lumipulse G p-tau 217/beta-amyloid 1-42 Plasma Ratio test, it measures the ratio of two proteins in the blood that reflect the buildup of amyloid plaques in the brain, one of the hallmarks of Alzheimer’s.
In a clinical study of 499 cognitively impaired adults aged 55 and older, 91.7% of people who tested positive on the blood test also had amyloid plaques confirmed by a brain scan or spinal fluid test. Among those who tested negative, 97.3% truly had no amyloid buildup. Less than 20% of patients received an indeterminate result. This test is not a standalone diagnostic tool, but it can help doctors decide whether more invasive or expensive testing (like a PET scan) is warranted.
Brain Imaging: MRI, CT, and PET Scans
Structural imaging with MRI or CT scans shows the physical shape and size of the brain. Doctors use these to look for brain shrinkage, evidence of strokes, tumors, or fluid buildup, all of which can cause or contribute to cognitive symptoms. These scans are a standard part of the specialist workup.
PET scans go a step further by revealing what’s happening at the molecular level. Amyloid PET scans use a tracer that binds to amyloid plaques. In a healthy brain, the tracer only shows up in white matter. In someone with significant amyloid buildup, the tracer extends into the outer brain tissue, with the earliest signal typically appearing in regions at the back and front of the brain. Results are measured on a standardized scale called Centiloids, where 0 represents a young, healthy brain and 100 represents the average person with mild to moderate Alzheimer’s. A scan is generally considered positive somewhere between 10 and 40 on that scale.
Tau PET scans work similarly but target a different protein, tau, which forms tangles inside brain cells. Tau buildup follows a predictable pattern: it starts in memory-related structures deep in the brain and gradually spreads outward into the temporal, parietal, and frontal regions as the disease advances. A scan showing spread beyond the inner temporal lobe is considered positive for an Alzheimer’s pattern. Another type of PET scan, called FDG-PET, measures how actively different brain regions are using energy. Some evidence suggests this can detect problems earlier than MRI in certain patients.
Spinal Fluid Testing
Cerebrospinal fluid (CSF) analysis can detect the same amyloid and tau proteins that PET scans look for. A sample is collected through a lumbar puncture, commonly called a spinal tap, where a needle is inserted into the lower back to draw a small amount of fluid. The procedure takes about 30 minutes and is done under local anesthesia. Some people experience a headache afterward that resolves within a day or two.
The lab measures ratios of specific proteins rather than individual levels. A ratio of phosphorylated tau to amyloid-beta above 0.023 is considered positive, meaning the result is consistent with amyloid buildup in the brain. A positive result doesn’t establish a diagnosis on its own, but it adds a significant piece of evidence. CSF testing has been a reliable option for years, though the newer blood tests may reduce how often spinal taps are needed going forward.
Genetic Testing
Genetic testing for dementia falls into two categories. Three rare gene variants, found on chromosomes 21, 14, and 1, directly cause early-onset Alzheimer’s, which develops before age 65 and sometimes decades earlier. If someone with symptoms has a strong family history of early-onset Alzheimer’s, a neurologist may order testing for these specific genes. Inheriting any one of them means the person has a very strong probability of developing the disease.
The more commonly discussed gene is APOE e4, which increases risk for late-onset Alzheimer’s and is associated with developing the disease at a younger age in certain populations. However, carrying APOE e4 doesn’t mean you’ll get Alzheimer’s, and not carrying it doesn’t mean you won’t. Because of this limited predictive power, APOE testing is primarily used in research settings to identify study participants rather than in routine clinical care. Genetic tests for dementia are not part of standard diagnostic workups unless family history strongly suggests a hereditary form.