Lasix is not a hormone compound but a diuretic. It belongs to the group of saluretics and to be exact is a loop diuretic. Lasix is a brand name for the drug furosemide, a very potent diuretic.Bodybuilders use Lasix shortly before a competition to excrete excessive, mostly subcutaneous, water so that they appear hard, defined, and ripped to the bone when in the limelight. The effect of tablets begins within an hour and continues for 3-4 hours. Depending on how much water is still in the athletes body he must have more or less frequent access to a restroom. This can cause a considerable weight loss within a very short time. For this reason, athletes often use Lasix to lose weight and to compete in a lower weight class.