Anemia (uh-NEE-me-uh) is a condition in which your blood has a lower than normal number of red blood cells. Anemia also can occur if your red blood cells don't contain enough hemoglobin (HEE-muh-glow-bin). Hemoglobin is an iron-rich protein that gives blood its red color.This protein helps red blood cells carry oxygen from the lungs to the rest of the body. If you have anemia, your body doesn't get enough oxygen-rich blood.As a result, you may feel tired or weak. You also may have other symptoms, such as shortness of breath, dizziness, or headaches. Severe or long-lasting anemia can damage your heart, brain, and other organs in your body.nemia has three main causes: blood loss, lack of red blood cell production, or high rates of red blood cell destruction. These causes might be the result of diseases, conditions, or other factors. Many types of anemia can be mild, short term, and easily treated.