Chemotherapy drugs can have different immunosuppressive effects and specifically reduce the number of white blood cells such as lymphocytes and leukocytes. Capecitabine is a new well-tolerated chemotherapy agent that is effective in treating certain cancers, especially breast cancer and gastrointestinal cancers such as colorectal, gastric and pancreatic cancers. Similar to other chemotherapeutics, capecitabine causes the formation of excess reactive oxygen species and a decrease in plasma antioxidant levels. It has been reported that capecitabine causes immune suppression and lymphopenia in cancer patients. Vitamin C, a well-known chelating agent with non-enzymatic antioxidant properties, repairs oxidative damage by reducing lipid peroxidation, altering the antioxidant defense system, showing electrons to free radicals, and extinguishing the reactivity of free radicals. These properties of vitamin C can provide very beneficial effects against organ damage. Vitamin C has been found to be beneficial for improving liver damage. Using vitamin C as an adjunct to minimize the toxic side effects of capecitabine can be helpful.