WARNING: This drug can cause serious (possibly fatal) harm to an unborn baby if used during pregnancy. Therefore, it is important to prevent pregnancy while taking this medication. USES: This medication is used to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. This product contains 2 medications, lisinopril and hydrochlorothiazide. Lisinopril is called an ACE inhibitor and works by relaxing blood vessels so that blood can flow through the body more easily. Hydrochlorothiazide is called a "water pill" (diuretic) and causes your body to get rid of extra salt and water. This effect may increase the amount of urine you make when you first start the medication.