How long does it take for alcohol to fully leave your system?

I’m asking because I couldn’t find a clear answer on Google and need some real-life answers.

I need to know because I planned an important medical checkup in the middle of my college introduction week (other dates weren’t available) and obviously I can’t have alcohol in my system when I get there.

I’m 20F with relatively low tolerance so we’re not talking about crazy amounts of alcohol.