Vitamin B12 (cobalamin) deficiency is a common cause of megaloblastic anemia, a variety of neuropsychiatric symptoms and elevated serum homocysteine levels, particularly in the elderly. There are a number of risk factors for vitamin B12 deficiency, including long-term use of metformin and proton pump inhibitors. No major medical organization, including the U. Preventive Services Task Force, has published guidance on screening for vitamin B12 deficiency in asymptomatic or low-risk adults, but high-risk patients, such as B. those with malabsorption disorders, can order a detection. The initial laboratory evaluation of a patient suspected of having vitamin B12 deficiency should include a complete blood count and serum vitamin B12 level. can be used to confirm deficiency in asymptomatic, high-risk patients with low normal vitamin B12 levels. Because crystalline formulations are better absorbed than natural vitamin B12, patients over the age of 50 and strict vegetarians should consume vitamin B12-fortified foods and vitamin B12 supplements rather than attempting to obtain vitamin B12 from dietary sources only Administering vitamin B12 to patients with elevated serum homocysteine levels has not been shown to decrease cardiovascular outcomes in high-risk patients or alter cognitive decline in patients with mild to moderate Alzheimer's disease.