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Your doctor may perform these tests to determine if you have signs of dementia, how severe the dementia is, or to look for other causes of dementia. These tests may include:

• Neurological exam—exam of the nervous system (brain, spinal cord, nerves, and muscles) for evidence of other neurological disorders.
• Psychological evaluation—to look for depression or other emotional illnesses that may be the first sign of Alzheimer’s disease.
• Neuropsychological evaluation—to test language, memory, reasoning, judgment, and orientation
• Mental status testing—to test memory, sense of time and place, and problem-solving abilities, attention span, language skills, visual spatial perception, learning capacity, judgement, insight, and decision making skills (often a part of the Neurological examination and Neuropsychologic testing)
• CT scan and MRI scan—these machines can take a detailed picture of your brain to identify any abnormalities
• PET scan —machine can take a detailed picture of your brain to identify any abnormalities
• Lumbar puncture (spinal tap)—to test the fluid surrounding the brain and spinal cord, may show infections that can cause dementia or show markers of Alzheimer's

Additionally, electroencephalogram (EEG) is a test that evaluates and follows the electrical activity of the brain. It is not a common test for evaluating most dementias but it may be done.

Blood and urine tests may be ordered to look for other conditions that cause dementia. The tests may include:

• Electrolytes (eg, sodium, potassium, and calcium)
• Thyroid function tests
• Complete blood count (CBC)
• Levels of vitamins (including B vitamins)
• Erythrocyte sedimentation rare (ESR)
• Lyme disease test
• HIV test
• Vasculitis work up

Genetic tests can look for markers that increase your risk for early-onset Alzheimer’s. Your doctor may recommend this test if you have family members with this condition.

An Alzheimer’s disease diagnosis usually falls into one of three categories:

• Probable Alzheimer’s disease—This indicates that other dementia-related disorders have likely been ruled out. The symptoms are most likely due to Alzheimer’s disease. At least two areas of cognition are affected. One area is a worsening of memory.
• Possible Alzheimer’s disease—The dementia is possibly caused by Alzheimer’s disease. There may be other disorders that are causing of the dementia.
• Definite Alzheimer’s disease—This diagnosis can only be made at the time of death. It is done through an autopsy when the brain tissue can be examined. This is the only way to diagnose the disease with complete certainty.