Furosemide (Lasix) is a diuretic (water pill) that's used to relieve swelling from extra fluids. It can also be used to lower blood pressure, either on its own or along with other blood pressure medications. Furosemide (Lasix) is taken by mouth, typically once or twice daily. It's available as an oral solution for people who've trouble swallowing tablets. Furosemide (Lasix) will cause you to urinate more often, so it's best to not take this medication too close to bedtime.