Vitamin C works rapidly, so the total amount we take over the day should be divided into multiple doses (four to six) or taken as a time-released tablet a couple of times a day. When increasing or decreasing vitamin C intake, it is best to do so slowly because our body systems become accustomed to certain levels. Some nutritionists describe a problem of rebound scurvy in infants, especially when a high amount is taken by the mother during pregnancy but then the infant gets very little after birth and so suffers some deficiency symptoms. I have seen nothing confirming this in the literature. Overall, though, it is probably wise to reduce vitamin C intake slowly after taking high amounts, rather than to drop abruptly.

My basic suggestion for vitamin C use is about 2–4 grams per day with a typical active and healthy city lifestyle. Based on previous levels in our native diets, Linus Pauling feels that the optimum daily levels of vitamin C are between 2,500 and 10,000 mg. Clearly, requirements for vitamin C vary and may be higher according to state of health, age (needs increase with years), weight, activity and energy levels, and general metabolism. Stress, illness, and injuries further increase the requirements for ascorbic acid. Many authorities suggest that we take at least 500 mg. of vitamin C daily to meet basic body needs.

During times of specific illnesses, especially viral infections, doctors who use megadose vitamin C treatment suggest at least 20–40 grams daily, some of it intravenously. Vitamin C has been used safely and effectively in dosages of 10 grams or more dripped slowly (over 30–60 minutes) into the blood to reach optimum tissue levels before excretion, so as to bathe the cells in vitamin C. Some doctors prescribe what is called "bowel tolerance" daily intake of vitamin C—that is, increasing the oral dose until diarrhea results and then cutting back. This level can vary greatly from a few grams to 100 grams or more. The claim is that our body knows what we need and will respond by changing the water balance in the colon when we have had enough. Physician Robert Cathcart has used vitamin C this way in his practice for years to treat many problems, with claimed good success; yet, I do not have the experience to make an adequate conclusion. This practice does, however, add further mystery to the vitamin C controversy. More research is definitely needed regarding ascorbic acid, and new discoveries will likely be made.