The medications you started taking as soon as you got the new kidney stop your body from rejecting it. Without them, your immune system would sense the kidney as foreign, just like a germ or virus, and try to fight or destroy it. To prevent this, you will take drugs to tone down (suppress) your immune system.

Ideally, you should be taking enough immunosuppressive medications to keep your body from attacking the new kidney, but not so much that you can’t fight off infections or other germs. Sometimes this balance gets thrown off (for example, if you start taking a drug that interferes with your immunosuppressive drugs, or if you’re sick). Of course, if you don’t take your medications, this will definitely result in rejection!