Lasix is used in the treatment of high blood pressure and other conditions that require the elimination of excess fluid (water) from the body. These conditions include congestive heart failure, cirrhosis of the liver, and kidney disease. When used to treat high blood pressure, Lasix is effective alone or in combination with other high blood pressure medications. Diuretics help your body produce and eliminate more urine, which helps lower blood pressure. Lasix is classified as a "loop diuretic" because of its point of action in the kidneys.