Background: Intravenous dosing is generally recognized to be the only effective means of maintaining a high concentration of vitamin C in the plasma. High dosing of vitamin C has been reported to be beneficial in, among other things, improving the quality of life as well as survival time of patients with terminal cancer. There is a paucity of information on the depletion of vitamin C in plasma at the high dosing regimen. Methods: The primary human-subject data reported by Levine et al. and Riordan et al. were used in this analysis. It is generally recognized that chemical kinetic studies could be used to deduce the underlying mechanism involved in the transport of vitamin C from the plasma into the cell structure. Results: A single rate constant was found to be essentially applicable to describe the rate of depletion of vitamin C from the plasma of healthy volunteers as well as for cancer patients, over the range of intravenous administration of 200 mg to 60,000 mg. Conclusion: The application of first-order reaction kinetics has been shown to provide a means to estimate the depletion time at any intravenous high dosing of vitamin C.