Hello, thanks for using health care magic. Anemia implies a decrease in the amount of hemoglobin ( oxygen transporting pigment) and there are various causes and types. Vitamin B12 deficiency is a common cause for a type of anemia known as megaloblastic anemia. Anemia implies a decrease in hemoglobin, as such reduced oxygen is supplied to muscles and other tissues, low energy production, production of lactic acid in muscles etc all these leading to a diversity of symptoms including fatigue. Vit b12 deficiency is caused by a nutritional deficiency or by an autoimmune disease where by antibodies destroy intrinsic factor necessary to absorb vit b12. Treatment is cause specific, oral supplementation plus increase consumption food rich in vit b2 in the case of deficiency or in vegeterians, intramuscular injections in people with absorption problems. Foods rich invit b12 include meat, eggs, sea food etc Best regards and hope this helps you. Dr. Achuo A. M.