Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials*

BACKGROUND: Vitamin B(12) deficiency is common, increasing with age. Most people are treated in primary care with intramuscular vitamin B(12). Several studies have reported equal efficacy of oral administration of vitamin B(12). OBJECTIVES: We set out to identify randomized controlled trial (RCT) evidence for the effectiveness of oral versus intramuscular vitamin B(12) to treat vitamin B(12) deficiency.