Merck Manual

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Vitamin C Toxicity

(Ascorbic Acid Toxicity)

By

Larry E. Johnson

, MD, PhD, University of Arkansas for Medical Sciences

Last review/revision Nov 2022
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Vitamin C plays a role in collagen, carnitine, hormone, and amino acid formation. It is essential for bone and blood vessel health and wound healing and facilitates recovery from burns. Vitamin C is also an antioxidant, supports immune function, and facilitates the absorption of iron (see table ).

The upper limit for vitamin C intake is 2000 mg/day.

Up to 10 g/day of vitamin C are sometimes taken for unproven health benefits, such as preventing or shortening the duration of viral infections or slowing or reversing the progression of cancer or atherosclerosis. Such doses may acidify the urine, cause nausea and diarrhea, interfere with the healthy antioxidant-prooxidant balance in the body, and, in patients with thalassemia or hemochromatosis, promote iron overload Overview of Iron Overload Typical adults lose about 1 mg iron (Fe) per day in shed epidermal and gastrointestinal cells; menstruating females lose on average an additional 0.5 to 1 mg/day from menses. This iron loss... read more .

Intake of vitamin C below the upper limit does not have toxic effects in healthy adults.

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