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 earning a doctoral degree in medicine and participating in clinical rotations. It's also common for medical school graduates to enroll in a residency program to study a specialty. Medical doctors need state licensure, and certification may also be required for some specialists.