Carter later returned in the season 15 episode, "The Beginning of the End", in which he rejoined the ER at County General. He explained to Cate Banfield that he was relocating to Chicago, and was looking to pick up some shifts. She agreed, after finding out that one of his teachers at the hospital was Mark Greene. He visited the Joshua Makalo Carter Center. At the end of the episode, it was shown that Carter was on dialysis because of amyloidosis developing from schistosomiasis which irreparably damaged Carter's remaining kidney. He was back in Chicago to be placed on the US transplant list. Working in the ER once again, he was shown to still be a good doctor with good judgment, but was still catching up with the latest medicines and techniques being used in the US. Eventually, his condition worsened, causing him to collapse while attending to a patient. While being treated by Dr. Gates and Dr. Morris, he goes into V-tach, but was brought back thanks to Morris's quick-thinking. He was then transferred to Northwestern Medical Center.