Either way, you need to see a doctor who will most likely prescribe you a diuretic. This can be Lasix or Furosemide and from experience I know those medications can be expensive. It most certainly wouldn't hurt to check for cheap lasix online after you have been given a prescription.
Lasix is the brand name for the diuretic, while Furosemide is a generic. You may want to read up on and get more information about furosemide. Both medications are pretty powerful in eliminating fluids and salt from the body and should not be used without a physician's advice and consent.
As with all medications, there are some side effects which can occur and it can interact with some drugs you are already taking for other conditions or you may need in the future. Even when you buy furosemide online, you can always consult a pharmacist about possible interactions.
You not only can, but should. And that goes for all meds you take!