How is M.D. used for doctors signatures?

The abbreviation "M.D." is used after a doctor's name to indicate that they have a Doctor of Medicine degree, which is the degree that is typically required to practice medicine in the United States. When a doctor signs their name, they may use the abbreviation "M.D." instead of writing out the full words "Doctor of Medicine". For example, if a doctor's name is John Smith and they have a Doctor of Medicine degree, they may sign their name as "John Smith, M.D."