Furosemide is one of the first medications used in acute heart failure to help remove excess fluid from the body. It works by acting on the kidneys, causing them to make more urine and helping relieve symptoms like shortness of breath and swelling. When given IV, it can start working within about 5 minutes, which makes it very useful in urgent situations when fluid needs to be removed quickly. It can also be used long-term to help control fluid buildup in chronic heart failure. Because it works through the kidneys, however, it can sometimes strain or worsen kidney function, so doctors usually monitor kidney labs while patients are taking it. Patients also commonly notice a lot of urination, which can be inconvenient but is part of how the medication removes excess fluid.