L-ascorbic acid, known as vitamin C, is one of the most studied vitamins today due to its extremely beneficial effects on the body. The human body cannot synthesize vitamin C and therefore it is necessary to take it daily through food through a variety of fruits and vegetables. Daily intake of vitamin C in a certain dose, but also intravenous administration, is the subject of numerous in vitro and in vivo studies. Such research is conducted with the aim of determining the antioxidant and prooxidative effect of this vitamin on the human body. Namely, as an antioxidant, vitamin C neutralizes free radicals by donating hydrogen and stabilizing them. Free radicals cause many dangerous diseases, and vitamin C helps to fight them. Apart from being an antioxidant, under certain conditions it also acts as a prooxidant because it produces hydrogen peroxide which is cytotoxic. This property is used in the treatment of cancer because hydrogen peroxide kills cancer cells without doing damage to healthy cells of the body. The aim of this work is to give a detailed overview and systematic insight in medicinal significance of vitamin C.