Anemia is a below-normal level of hemoglobin or hematocrit in the blood. Hemoglobin is the protein in red blood cells that carries oxygen to all parts of the body. People with mild anemia may not have any symptoms or may have only mild symptoms. People with severe anemia may have problems carrying out routine activities and can feel tired or experience shortness of breath with activity. The chance of developing anemia increases as kidney disease gets worse. Diseased kidneys may not produce enough erythropoietin (EPO), a hormone that regulates red blood cell production. Less EPO leads to lower red blood cell counts. Other factors that can contribute to anemia in patients with kidney disease include iron deficiency, some vitamin deficiencies, and the effects of poor nutrition or inflammation.