Although vitamin C is an essential nutrient you need for healthy cells and proper immune function, too much of it can cause unpleasant side effects. Taking too many vitamin C tablets may result in upset stomach, abdominal cramps and diarrhea. Vitamin C supplements in any dosage may also interfere with cholesterol and cancer medications, according to the Office of Dietary Supplements. Talk to your doctor before taking any nutritional supplements.
Recommended Vitamin-C Intake
Medline Plus recommends that women get 75 milligrams of vitamin C per day, and that men get 90 milligrams per day. The site also reports that taking more than 2,000 milligrams per day will likely cause side effects. Whole foods such as citrus fruits, cantaloupe, broccoli and bell peppers are the best sources of vitamin C, and deficiency is rare in the United States. In addition, Medline Plus claims that supplements are not shown to speed recovery from colds or flus when taken after the illness strikes.