 [ Symptoms ] do i need to worry about taking supplements if i am on chemotherapy [ Disease ] vitamins minerals and herbal supplements may interact with chemotherapy drugs or radiation treatments blocking their effectiveness there is even some reason to worry that antioxidant supplements may protect cancer cells although it is controversial still it is very important for you to tell your doctor about any supplements that you currently take it is just as important to talk to your doctor before starting on any new supplements while you are undergoing cancer treatment of any kind