Diuretics (often called water pills) are drugs that cause the body to rid itself of excess fluids and sodium through urination. Excess fluid in the body can lead to high blood pressure. This helps to relieve the heart’s workload and also decreases the buildup of fluid in the lungs and other parts of the body, such as the ankles and legs. Different diuretics remove fluid at varied rates and through different methods. They are used to treat high blood pressure, congestive heart failure and some congenital heart defects.