Vitamin B-12 Deficiency: Recognition and Management

摘要

Vitamin B-12 deficiency is a common cause of megaloblastic anemia, various neuropsychiatric symptoms, and other clinical manifestations. Screening average-risk adults for vitamin B-12 deficiency is not recommended. Screening may be warranted in patients with one or more risk factors, such as gastric or small intestine resections, inflammatory bowel disease, use of metformin for more than four months, use of proton pump inhibitors or histamine H-2, blockers for more than 12 months, vegans or strict vegetarians, and adults older than 75 years. Initial laboratory assessment should include a complete blood count and serum vitamin B-12 level. Measurement of serum methylmalonic acid should be used to confirm deficiency in asymptomatic high-risk patients with low-normal levels of vitamin B-12. Oral administration of high-dose vitamin B-12 (1 to 2 mg daily) is as effective as intramuscular administration for correcting anemia and neurologic symptoms. Intramuscular therapy leads to more rapid improvement and should be considered in patients with severe deficiency or severe neurologic symptoms. Absorption rates improve with supplementation; therefore, patients older than 50 years and vegans or strict vegetarians should consume foods fortified with vitamin B-12 or take vitamin B-12 supplements. Patients who have had bariatric surgery should receive 1 mg of oral vitamin B-12 per day indefinitely. Use of vitamin B-12 in patients with elevated serum homocysteine levels and cardiovascular disease does not reduce the risk of myocardial infarction or stroke, or alter cognitive decline. Copyright (C) 2017 American Academy of Family Physicians.