Wednesday’s Ask Dr. Walt — Vitamin C

Dear Dr. Walt

Is it possible to take too much vitamin C?

—Citrus Fan in California

Dear Ascorbic Acid Admirer,

According to the experts at, “Yes, it’s possible to take too much vitamin C. Since vitamin C is water-soluble (excess amounts are excreted and do not accumulate in the body), people sometimes assume there is no harm in taking large doses.

However, there are potential short-term and long-term problems with taking high doses (500 to 1,000 mg per day) or very high doses (more than 2,000 mg per day) of vitamin C.”

For example, very high doses of vitamin C can cause gastric discomfort and diarrhea. In fact, this is the basis for the FDA current upper tolerable daily intake limit of 2,000 mg for adults.

There are also concerning reports suggesting potential problems with daily doses of just 500 to 1,000 mg of vitamin C (keep in mind that the recommended daily intake of vitamin C for adults is only 75 mg to 120 mg, with an additional 35 mg for smokers).

For example, while long-term, low-dose supplementation with vitamin C may help to prevent cataracts, high doses may actually increase the risk.

Taking several hundred milligrams of vitamin C daily may also hamper some of the benefits of endurance exercise, as has been found with high doses of other antioxidant vitamins and supplements.

High doses of vitamin C may also reduce the effectiveness of certain medications and increase the risk of liver damage when taking high doses of acetaminophen (Tylenol).

Lastly, high doses may also interfere with some lab tests (for cholesterol, blood sugar, and blood in the stool, for example).

So, what do I tell my patients? Do notexceed the recommended upper limit of daily intake of 2,000 mg daily.

Dr. Walt

© Copyright WLL, INC. 2018. This blog provides a wide variety of general health information only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment from your regular physician. If you are concerned about your health, take what you learn from this blog and meet with your personal doctor to discuss your concerns.
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