I see a cardiologist who specializes in POTS, but most cardiologists can diagnose and treat you. You just have to find a good one because some cardiologists don't know much about POTS or dismiss your symptoms. Mine gave me midodrine which has helped immensely. They can also schedule regular IV fluids if your case is severe, you don't respond to medication immediately, or you're having issues getting enough fluids

My neurologist is the one who diagnosed me and sent me to the cardiologist.

My PCP was the one who caught it, she sent me to a cardiologist to get an official diagnosis. I have very low blood pressure so they didn't want to put me on midodrine because it lowers BP as well as HR. So they just had me up my fluid and salt intake for now