Hair loss is a common side effect of chemotherapy, and it can be a distressing experience for cancer patients after having gone through cancer treatment. Hair loss typically starts 2-4 weeks after beginning chemotherapy. It may continue to thin gradually or fall out in clumps. It's a good idea to prepare mentally for this process. Using the same shampoo that you normally use for your hair type may be no longer be suitable as your hair and scalp changes during and after treatment.