Functional implications of vitamin B(12) deficiency.

Vitamin B(12) deficiency is a common but underrecognized problem in older adults. Historically, B(12) deficiency was diagnosed once a severe pernicious anemia developed. Scientific developments have led to a new understanding of a broader spectrum of B(12) deficiency and identification of a milder form of deficiency associated with food/vitamin B(12) malabsorption. Using an individual example, this article describes the functional impact of vitamin B(12) deficiency and highlights modern approaches to diagnosis and treatment.