Lasix is a loop diuretic that prevents your body from absorbing too much salt, allowing the salt to be passed in the urine.

Furosemide is a loop diuretic. Loop diuretics act on the Na+-K+-2Cl- symporter (cotransporter) in the thick ascending limb of the loop of Henle to inhibit sodium and chloride reabsorption. This is achieved by competing for the Cl- binding site. Because magnesium and calcium reabsorption in the thick ascending limb is dependent on sodium and chloride concentrations, loop diuretics also inhibit their reabsorption.