A healthcare provider typically prescribes Diovan HCT^® (valsartan and hydrochlorothiazide) to lower blood pressure in adults. Diovan HCT is a combination of two medications -- Diovan and hydrochlorothiazide. Diovan helps to relax the blood vessels to allow more blood to flow through them, while the hydrochlorothiazide causes the kidneys to remove more salt and water from the blood in order to reduce the blood volume. The combined effects of these two medications have been shown to cause a greater drop in blood pressure than if either medication was used by itself. By lowering blood pressure, Diovan HCT can lower the risk of developing health problems, such as a heart attack or stroke, that are caused by long-term high blood pressure. Diovan HCT comes as a tablet usually taken once daily. Some factors that can affect Diovan HCT dosage include other medical conditions you may have, how you respond to Diovan HCT, and other medications you may be currently taking.