Losartan blocks receptors in your body that normally bind to a hormone called angiotensin II. When angiotensin II binds to these receptors, it causes your blood vessels to constrict and the body to release a hormone that tells your kidneys to keep sodium. Blocking these receptors help your blood vessels relax so that blood can move through them more easily. Blocking these receptors also causes your body to get rid of sodium and water. These effects can help your heart work better, lower blood pressure, and may reduce your risk for heart attack, stroke, and kidney damage progression.