The liver is an organ located in the upper right side of the abdomen and it is part of the digestive system. It performs several life-sustaining functions: it processes nutrients, produces proteins, stores sugar or glycogen, and it also controls the body's hormone levels, blood sugar levels, cholesterol levels, and fluid retention. The liver filters unwanted substances and helps the body fight infection. Hepatitis is a virus that travels through the blood stream and attacks the liver. There are several types of hepatitis, with hepatitis C being the most damaging form. The hepatitis virus causes the liver to become inflamed. Healthy cells are replaced with scar tissue, leaving the liver unable to function normally. Immunization is available for some forms of hepatitis; for example, vaccination against hepatitis B is routinely given to infants in the USA. However, if a person becomes infected with any of the hepatitis viruses, a doctor may prescribe medication to relieve some symptoms of the disease. It is also important for infected persons to avoid alcohol and certain medications that can cause additional damage to the liver.