What happens when you have chemotherapy? Chemotherapy can affect some normal areas of the body as well as the tumor. After someone gets chemotherapy, they may not feel like eating and they may have an upset stomach for the rest of the day. They may also feel more tired than usual. People on chemotherapy can't fight off infection very well. If they get a fever, they need to come to the hospital to get special medications. Once the chemotherapy is stopped, all of these things usually get better. Sometimes, feeling better takes a few weeks or a few months, so you need to give yourself time. Answered by Dr. Regina Jakacki, pediatric oncologist, Children's Hospital of Pittsburgh July, 2007