Is It Safe to Take Megadoses of Vitamin C?

How much vitamin C is safe? Find out the risks of taking megadoses of vitamin C – and how to get this vitamin naturally.

Taking megadoses of vitamin C was once popular – as a way to ward off colds and flu. Unfortunately, the most recent studies show that taking megadoses of vitamin C doesn’t prevent colds at all, although vitamin C is important for a healthy immune system. Despite proof that it’s effective, some people still take vitamin C supplements from their health food store in hopes it will help them stay healthy. Is this a good idea? How much vitamin C is safe?

How Much Vitamin C is Safe?

The current RDA for vitamin C is 90 milligrams for men and 75 milligrams for women. This is the amount of vitamin C needed to prevent the vitamin C deficiency disease called scurvy. Because vitamin C is an antioxidant vitamin and plays a role in immunity and building healthy collagen, it’s a good idea to get a little more than the RDA – but taking megadoses of vitamin C isn’t necessary for good health. Unfortunately, it’s not entirely clear how much vitamin C per day is ideal.

What Happens if You Get Too Much Vitamin C?

It’s hard to get too much vitamin C through diet, and most people have to make a conscious effort to even get enough of this important vitamin. Vitamin C is unstable and easily broken down by the heat of cooking, so the best sources are raw fruits and vegetables. Eating citrus fruits, kiwi, green peppers, strawberries, cauliflower, and broccoli are some of the better ways to get vitamin C. When people get too much vitamin C, it’s usually by taking supplements.

The risks of taking even megadoses of vitamin C are pretty low. Vitamin C is water-soluble, so the excess is filtered by the kidneys and released into the urine. It’s not stored by the body and doesn’t build-up to toxic levels. Taking megadoses of vitamin C can have side effects – although none are life-threatening. Excess vitamin C is converted to oxalates, which can increase the risk of calcium oxalate kidney stones in some individuals.

Too much vitamin C can also cause diarrhea and stomach upset. Vitamin C enhances iron absorption, which isn’t necessarily a good thing for men and post-menopausal women. Taking megadoses of vitamin C can also decrease the absorption of copper.

How Much Vitamin C is Safe: The Bottom Line?

Because vitamin C is water-soluble, it’s difficult to get too much unless you take megadoses of vitamin C. Even then, it’s unlikely to cause life-threatening problems. Still it’s best not to take vitamin C in supplement form, but, instead, get it through a diet rich in raw fruits and vegetables. Too much vitamin C causes diarrhea and interferes with copper absorption – and the benefits of taking megadoses of vitamin C still haven’t been proven. Whenever possible, get your vitamin C naturally through diet.


The Nutritionist. Robert Wildman, PhD, RD. 2002. pages 201-204.

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  1. Thanks, for sharing

  2. Thanks for sharing.

  3. In the past I would take 2-4,000 mg of Vitamin C every other day. My family has adjusted our diets and have cut back to a single multivitamin each; daily.

    My parents always told me to pay the farmer; not the doctor.

    Great article.

    Eric Pinola

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