Aetna Intelihealth
Aetna: Inteli Health: Vitamin B12 Deficiency
Thorough overview of vitamin B12 deficiency. Includes information on symptoms, treatment, prevention, and much more.
US National Library of Medicine
Medline Plus: Anemia and Vitamin B 12
This site discusses anemia due to an insufficinency of B-12. It discusses the absorption problems of B-12 as well. Lastly it reveals what researchers have discovered is the best way to absorb B-12 into the body.