Doctors may use a variety of laboratory tests to help diagnose dementia and/or rule out other conditions, such as vitamin deficiency or hormone balance, that can contribute to symptoms. A partial list of these tests includes a complete blood count, blood glucose test, urinalysis, drug and alcohol tests (toxicology screen), cerebrospinal fluid analysis (to rule out specific infections that can affect the brain), and analysis of thyroid and thyroid-stimulating hormone levels. A doctor will order only the tests that he or she feels are necessary and/or likely to improve the accuracy of a diagnosis. Additional tests may also include B12 level and analysis of thyroid and thyroid-stimulating hormone levels. Blood counts, tests for kidney, liver, or blood glucose problems, drug and alcohol tests (toxicology screen), tests for certain infections known to cause dementia, such as HIV and syphilis, and other tests may be ordered as appropriate for a patient’s specific situation. Sometimes, a lumbar puncture (spinal tap) may be performed to obtain cerebrospinal fluid, which is then analyzed for evidence of Alzheimer’s disease proteins or of certain infections, inflammatory conditions, or other diseases that may cause dementia. A doctor will order only the tests that he or she feels are necessary and/or likely to improve the accuracy of a diagnosis.