One can buy 1000mg vitamin C in tablet form, where an adult dosage can be 3000mg – 10,000mg daily for three weeks, then reduce the amount to 2000mg -3000mg, but do seek professional guidance when taking higher doses.
One can take oral doses of vitamin C to beat some cancers, for instance ascorbic acid. Lypo-spheric acid or calcium ascorbate powder can all be purchased from your chemist or health food store. More in the main article.