What is telmisartan/hydrochlorothiazide used for? Telmisartan/hydrochlorothiazide is used for the treatment of high blood pressure in adults. The medication is composed of an angiotensin II receptor blocker and a diuretic, which, when combined, control high blood pressure better than either medicine used alone. Telmisartan/hydrochlorothiazide is currently not approved for use in children, nor are there any off-label uses at this time.