Anemia is a condition marked by a person’s inability to produce adequate amounts of healthy red blood cells, which deliver oxygen to bodily tissues. It can be caused by a number of nutritional deficiencies, including iron, folate and vitamin B12. However, anemia can also result from abnormalities in the bone marrow and blood system, and it can be triggered by pregnancy, certain medications and the presence of chronic diseases including rheumatoid arthritis, cancer, kidney disease and colitis. Symptoms can range from mild to severe, and include mood changes, headaches, difficulty concentrating, changes to eye or skin color, a sore tongue and lightheadedness.