Vitamin C Supplements

©2007 Publications International, Ltd. Vitamin C supplements can be problematic if effects.

Due to the influx of news surrounding the benefits of vitamin C, many people feel that when it comes to vitamin c supplements, more is automatically better.  While vitamin C supplementation is generally safe, even in larger doses, it can interact negatively with other nutrients in the body, if certain pre-existing health conditions are present.

So, what about these high doses of vitamin C -- are they without consequence? Typically, 500 to 1,000 mg per day are sufficient for general health enhancement. Doses of 1,000 to 3,000 mg (1 to 3 g) per day may be indicated for treating specific acute conditions. Amounts larger than this, especially over long periods of time, can have adverse effects such as cramps, diarrhea, and destruction of vitamin B12, and decreased copper absorption.


Since vitamin C increases the amount of iron that gets absorbed, this can be a problem for people who have hemochromatosis, an iron-overload disease in which an inherited defect allows too much iron absorption.

Other cautions about excessive doses of vitamin C include:

  • Gout patients can have greater problems with uric acid.
  • Those with sickle-cell anemia have a more fragile red blood cell that excess vitamin C breaks apart. People with this inherited condition should not take large amounts of vitamin C.
  • Chewable vitamin C tablets can erode tooth enamel if used on a regular basis. Buffered chewable tablets are less damaging.
  • High doses might lead to rebound scurvy when the supplements are suddenly stopped. The body develops a mechanism for breaking down and excreting the vitamin quickly, so that a deficiency may develop when you resume a lower intake. To be safe, people taking large amounts of vitamin C should wean themselves gradually from it rather than stopping abruptly. The body can then become accustomed to lower intakes. There have been reports of laboratory animal offspring, most notably guinea pigs, who developed rebound scurvy after their mothers took large amounts of vitamin C during pregnancy. After birth, these guinea pigs no longer had the large doses, yet they were very efficient at clearing vitamin C from their systems; as a result, a deficiency developed.  This same effect is unlikely to happen in human babies, especially if their mothers breastfeed for at least one month after the birth.
  • Vitamin C can interfere with glucose tests since these two compounds have similar chemical structures. Physicians need to know if you are taking large doses of vitamin C so that they won't misinterpret laboratory tests for the presence of glucose in the urine. This can also create problems for people with diabetes who need to monitor blood glucose levels.
  • Large amounts of vitamin C can cover up the presence of blood in the stool, distorting the results of tests designed to detect colon cancer.

The moral of the story is to know when and how much supplementation is best based on your own health and history.  Vitamin C is a great nutrient in our arsenal against disease, but too much or in the wrong form over a long period of time can cause problems. Use vitamin C wisely. Supplementation in amounts from 200-2000 mg per day is fine for most people, particularly in the buffered forms, going up to 10,000 mg per day when fighting an illness. If you're looking for the best prices on vitamin C supplements, click here.

For more information on Vitamin C, check out the links below:

  • Learn about the healing power of vitamin C by reading Benefits of Vitamin C.
  • If you're worried you're not getting enough Vitamin C in your diet, visit Vitamin C Deficiency.
  • Fortunately, Vitamin C is abundant in many food sources, to find out which are your best bets check out Foods That Contain Vitamin C.
  • To find out more about Vitamin C in general, check out What Is Vitamin C?
  • To learn about the many vitamins in our diet, how much you should be eating, and where to find them, go to our general Vitamins page.
  • To find the best prices on vitamin C supplements, click here.

ABOUT THE AUTHOR:Jennifer Brett, N.D. is director of the Acupuncture Institute for the University of Bridgeport, where she also serves on the faculty for the College of Naturopathic Medicine. A recognized leader in her field with an extensive background in treating a wide variety of disorders utilizing nutritional and botanical remedies, Dr. Brett has appeared on WABC TV (NYC) and on Good Morning America to discuss utilizing herbs for health.