Hello, I Was Prescribed Hydrochlorothiazide Twice A Day For Minere

hello, I was prescribed hydrochlorothiazide twice a day for minere disease in September, 2015. My concern is that this medication is also a high blood pressure medication. I have always had low blood pressure 90/60 even when pregnant. How does this medication affect a person with low blood pressure. My ENT claims I can take this up to 4 times a day. Recently, I am very nauseated and am experience headaches.