Lasix is a brand name for the drug furosemide, a very potent diuretic. Technically Lasix belongs to a class of drugs known as loop diuretics, which will cause the body to excrete water as well as potassium, sodium and chloride. Loop diuretics including Lasix are among the strongest such drugs available, having an extremely dramatic effect on fluid levels in the body. Potassium levels need to be particularly watched, Lasix greatly increasing the amount excreted. The use of a prescription potassium supplement therefore is often required to keep levels in balance, otherwise a serious heart complications might develop. Mistakes in potassium dosage have equally serious consequences, so Lasix is clearly a risky item to use. But when an athlete needs to shed water, it is very difficult to find something like Lasix that works better. Athletes use diuretics including Lasix for a couple of specific purposes. Competitive athletes use Lasix to drop water weight, in an effort to make adjustments in their weight class standings. Since the weigh-in is most often a day or days before a competition/match, one can drop their bodyweight considerably and be back to normal within hours after rehydration. Use of Lasix logically seems to provide an unfair advantage, the athlete competing at a much heavier weight than believed. This advantage of Lasix is only offset by the now near universal nature of this practice. Bodybuilders also rely heavily on Lasix when preparing for a contest. It can efficiently lower subcutaneous water concentrations, helping to produce that super-ripped look so common on stage today.