People who have a doctor's degree may use the title "doctor", though in practice it is often used only by medical doctors. Medical doctors examine, diagnose and treat patients. They can specialize in a number of medical areas, such as pediatrics, anesthesiology or cardiology, or they can work as general practice physicians. Becoming a medical doctor requires a doctoral degree in medicine and participating in clinical training. Medical doctors need a licence, and certification may also be required for many specialists. 