American employers typically have a policy regarding sick days. Most of the places I've worked require a note from a doctor for absences of three consecutive days or more, and they can also request one in other circumstances like "excessive absences" or whatever. The note usually just says, "flourish was seen in my office on Monday May 1st" or "flourish is advised to be on bed rest for this many days," or "flourish is restricted to lifting no more then ten pounds due to a medical condition."
We pay for the appointment, not the note, and some doctors will do a note without an office visit, depending on history and situation. Like last winter I had a horrible infection which was very painful so at one point I emailed my doctor and he faxed something to my employer so I wasn't required to perform one certain duty due to pain and the possibility of a rupture kinda thing. HTH