Does a doctor need a doctorate degree?

.... to do what, exactly? Be a doctor?

To be called "Dr.", all you need is a doctoral degree. This can take anywhere from six to ten years depending on a number of factors, and can relate to any field of science, not just medicine. Generally speaking, people earn a Bachelors degree first (3-5 years), then a Masters (1-3 years), then their Doctorate (1-4 years).

If you mean what degrees does a medical doctor obtain, that's a be different. A medical doctor starts out by earning a regular, 4-year degree like every other professional. Then comes four years of medical school. Then it depends on if you want to specialize. If you do, it's between 3 and 8 more years learning and working in a hospital before you're fully trained.