The number of posts on here of people telling their employer the exact reasons they are sick or absent is disturbing.
You are under no obligation to give the exact reason you need medical treatment. You're just giving them information to use against you later.
When I write work notes, I can not put the reason someone is seen in the ER or hospitalized.
Obviously, there are some exceptions but those exceptions do not apply to most of the posts on here.
Here is more information below.
https://www.hhs.gov/hipaa/for-individuals/employers-health-information-workplace/index.html