Anemia is a disease of the blood. Anemia is characterized by a deficiency in red blood cells or in the concentration of hemoglobin in the body. These deficiencies are caused by either decreased production or increased destruction of blood cells. Anemia is most common among women in their reproductive years, infants, and the elderly. Because one of the major functions of red blood cells is to transport oxygen, a decrease in red blood cells decreases the amount of oxygen delivered to the body's tissues, which results in the symptoms of anemia.

Iron deficiency anemia is the most common form of anemia. Approximately 20% of women, 50% of pregnant women, and 3% of men are iron deficient. Iron is an essential component of hemoglobin. Iron is normally obtained through the food in the diet and by the recycling of iron from old red blood cells. High-risk groups include: women of child-bearing age who have blood loss through menstruation; pregnant or lactating women who have an increased requirement for iron; infants, children, and adolescents in rapid growth phases; and people with a poor dietary intake of iron through a diet of little or no meat or eggs for several years.

Folate or folic acid is necessary for red blood cell formation and growth. Dietary sources of folate are found in green leafy vegetables and liver. Because folate is not stored in the body in large amounts, a continual dietary supply of this vitamin is needed.

In folate deficiency anemia, the red cells are abnormally large and are referred to as megalocytes, and in the bone marrow as megaloblasts. Subsequently, this anemia may be referred to as megaloblastic anemia. Causes of the anemia are poor dietary intake of folic acid as in chronic alcoholism, malabsorption diseases such as celiac disease and sprue, and certain medications. Deficiencies due to increased need for folic acid may occur in the third trimester of pregnancy. Risk factors are a poor diet, overcooking food, alcoholism, having a history of malabsorption diseases, and pregnancy.

Vitamin B12 is essential for normal nervous system function and normal red cell, white cell and platelet production. All sources of vitamin B12 come from the diet in animal products, including dairy and eggs. Causes of vitamin B12 deficiency include a strict vegetarian diet excluding all meat, fish, dairy products, and eggs and chronic alcoholism. Anemia of B12 deficiency that is caused by a poor diet can be prevented through a well-balanced diet. Use of vitamin B12 injections can prevent deficiency after surgeries known to result in vitamin B12 deficiency.

There is a great difference between individuals as to when symptoms of anemia develop. Some common symptoms are: