It’s no secret that the Grey’s Anatomy doctors are not the most ethical physicians, and Izzie, in particular, should have been fired multiple times.
Grey's Anatomy is oftentimes closer to a soap opera than a primetime network television show, which is made clear by the number of times the characters should have been fired from their jobs at Seattle Grace Hospital. In particular, Izzie Stevens, played by Katherine Heigl, broke eight rules during her time on the ABC medical drama series, which should have resulted in her being removed from the hospital. However, Grey's Anatomy is a fictional show in its own universe with its own set of rules, meaning that the penalty for breaking some regulations in the series isn't the same as in the real world.
Of course, throughout the series' 19 seasons, characters have gotten in trouble and even been fired. If there were no consequences for their actions, then the show would not contain any real conflict, resulting in a boring program that undoubtedly would not have lasted as long as it has. Even Izzie was reprimanded a few times throughout the six seasons she was on Grey's Anatomy, but given her track record, she should have never kept her job as long as she did.