Research has shown that there are specific blood or tissue concentrations of certain nutrients that must be achieved in order for them to be pharmacologically active. Vitamin C is a good example of such a nutrient. Numerous studies show high concentrations of Vitamin C are required in the serum and intracellular fluid before it can exert its beneficial effects.
These high concentrations simply cannot be achieved by taking the nutrients orally; the bulk of vitamins and minerals
swallowed in pill or liquid form is excreted, with very little actually absorbed into the bloodstream. Complicating this further is that many patients have conditions that impair their intestinal absorption in the first place. Finally, as noted above, many patients cannot tolerate high doses of certain vitamins and minerals because these upset their stomachs. Therefore, only intravenous vitamin therapy can directly deliver pharmacologically effective doses of the required nutrients.