routine labs: complete blood count, fasting blood sugar, thyroid stimulating hormone, calcium, electrolytes, urea and creatinine
specific labs: B12, folate levels, liver function tests
for most patients who have a clinical presentation consistent with AD with typical cognitive symptoms or presentation, only the above basic set of tests need to be completed
extensive investigations are not required unless a reversible cause of dementia is suspected 
Computerized Tomography (CAT): role in detecting certain causes of dementia such as VaD, tumor, NPH or subdural hematoma
Magnetic Resonance Imaging (MRI): helps to visualize white matter lesions
Functional Imaging: Positron Emission Technology (PET scans) and Functional Magnetic Resonance Imaging (fMRI): mainly used for research purposes only and not in clinical settings
EEG: used in patients in whom seizure disorder is suspected
lumbar puncture to analyze the cerebrospinal fluid (CSF): used to rule out infection, inflammation, malignancy
in complex cases, a referral to specialists such as geriatrics, psychogeriatrics or neurology may be required
How well do you know your diagnostic tools ?
8. Patterson CJS, Gauthier S, Bergman H, Cohen CA, Feightner JW, Feldman H, Hogan DB. The recognition, assessment and management of dementing disorders: conclusions from the Canadian Consensus Conference on Dementia. Canadian Medical Association Journal 1999; 160 Suppl 12:S1-15.