Chemotherapy is commonly used anti-cancer medication. It usually administered through injection into a vein though oral forms of chemotherapy are becoming more prevalent.  There has been debate for more than a decade over whether vitamin C supplements are useful or harmful for cancer patients. Since vitamin C is an antioxidant some researchers are of the view that it helps cancer patients.  Improvement in survival however has never been demonstrated in controlled studies.  Medical oncologists are in general of the view that antioxidants decrease the effectiveness of chemotherapy.