Ascorbate (ascorbic acid, vitamin C) is one of the early, unorthodox treatments 
for cancer. The evidence upon which people base the use of ascorbate in cancer 
treatment falls into two categories: clinical data on dose concentration 
relationships, and laboratory data describing potential cell toxicity with high 
concentrations of ascorbate in vitro. Clinical data show that when ascorbate is 
given orally, fasting plasma concentrations are tightly controlled by decreased 
absorption, increased urine excretion, and reduced ascorbate bioavailability. In 
contrast, when ascorbate is administered intravenously, concentrations in the 
millimolar level are achieved. Thus, it is clear that intravenous administration 
of ascorbate can yield very high plasma levels, while oral treatment does not.