This review discusses the chemical and biological properties of ascorbic acid (vitamin C), highlighting its roles as an antioxidant and pro-oxidant. Ascorbate, a water-soluble reducing agent, plays a crucial role in maintaining cellular redox balance and protecting against oxidative stress. It acts as a cofactor for various enzymes, including hydroxylases and dioxygenases, and is involved in collagen synthesis and gene expression regulation. The review also explores the potential of pharmacological ascorbate, particularly intravenous administration, in cancer treatment. High doses of ascorbate can bypass the gut's tight control mechanisms, leading to elevated plasma levels and the production of hydrogen peroxide (H₂O₂). This H₂O₂ can act as a prodrug, delivering significant amounts to tumors. The review discusses the mechanisms by which ascorbate's antioxidant and pro-oxidant properties influence its therapeutic effects, emphasizing the importance of catalytic metal ions in determining its behavior. Additionally, it reviews the historical use of high-dose ascorbate in cancer treatment and the need for further research to optimize its use in clinical settings.This review discusses the chemical and biological properties of ascorbic acid (vitamin C), highlighting its roles as an antioxidant and pro-oxidant. Ascorbate, a water-soluble reducing agent, plays a crucial role in maintaining cellular redox balance and protecting against oxidative stress. It acts as a cofactor for various enzymes, including hydroxylases and dioxygenases, and is involved in collagen synthesis and gene expression regulation. The review also explores the potential of pharmacological ascorbate, particularly intravenous administration, in cancer treatment. High doses of ascorbate can bypass the gut's tight control mechanisms, leading to elevated plasma levels and the production of hydrogen peroxide (H₂O₂). This H₂O₂ can act as a prodrug, delivering significant amounts to tumors. The review discusses the mechanisms by which ascorbate's antioxidant and pro-oxidant properties influence its therapeutic effects, emphasizing the importance of catalytic metal ions in determining its behavior. Additionally, it reviews the historical use of high-dose ascorbate in cancer treatment and the need for further research to optimize its use in clinical settings.