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A 21-year-old member asked:

Are there negative side effects to taking large doses of slow release vitamin c to avoid colds?

8 doctor answers16 doctors weighed in
Dr. Padmavati Garvey
A Verified Doctoranswered
A US doctor answeredLearn more
Yes: There are negative side effects to taking too much of any vitamin. It is debatable if vitamin C supplements even work in preventing colds. Our body needs minute amounts of vitamins. Taking more vitamins does not mean your body will work better. You are better off eating and orange and washing your hands frequently.
Dr. Philip Rosenblum
Family Medicine 28 years experience
I absolutely agree with this answer. I have seen a large number of patient's taking 1000-2000 mg of vitamin C daily for years, complaining of heartburn and other gastro-intestinal complaints also for years. Stop the Vitamin C and many of these symptoms will recede. Most people fail to recognize side effect from their supplements, but worry tremendouly about them in a prescription medication.
Dec 29, 2011
Dr. Sheila Goodman
Specializes in Obstetrics and Gynecology
No: High doses of vitamin C are unlikely to hurt anything since you'll just put any extra c into your urine. On the other hand, high dose c has been shown to have no effect in preventing colds. The best way to avoid colds is frequent hand washing.
Dr. Kathryn Mercer
Obstetrics and Gynecology 34 years experience
No: There really isn't any huge harm in taking too much vitamin C as it is water soluble, and what you don't absorb will be excreted in your urine. On the other hand, there isn't much evidence that it prevents disease.
Dr. Nicole Bullock
Obstetrics and Gynecology 17 years experience
A good multivitamin / prenatal vitamin will also help with your overall immune health. Vit D and DHA (=omega 3 = fish oil) are also good for the immune system. Don't forget the basics .... drink plenty of water, get good sleep, wash your hands and avoid contact with sick people!
Nov 21, 2011
Dr. Megan Bird
Obstetrics and Gynecology 19 years experience
Yes: Some women who take high dose vitamin C get diarrhea from it. Otherwise it is pretty low risk.
Dr. Raj Syal
Dr. Raj Syalanswered
Obstetrics and Gynecology 33 years experience
Yes: Mega doses of any vitamin is not recommended. The benefits are not proven and marginal at best. A good multi vitamin should suffice.
Dr. Vasu Brown
Integrative Medicine 34 years experience
Creates kidney stone: If the body pH is acidic you can test this by urine or saliva litmus test and this is not in the normal range between 6.8-7.4 then you need to make sure before you take vitamin c your body is in alkaline range. Otherwise you can potentially create kidney stones and calcify other areas too. Vitamin c can be used upto 1000mg per day for colds and vitamin c flush high dose done for constipation.
Dr. Lawrence Rosen
Pediatrics 28 years experience
Yes but mild: Typically large doses of vitamin c are well tolerated as long as you're well hydrated - GI adverse effects like diarrhea or nausea can occur at very high doses.
Dr. Michael Rothman
Internal Medicine 35 years experience
Yes: Mega dose vitamin c can actually be dangerous. It is true that vitamin c is water soluble & you will excrete any vitamin c that you don't use. However, in order to excrete vitamin c in your urine, you must also excrete minerals as well. Therefore, excess vitamin c can lead to mineral deficiencies, especially a copper deficiency. Be very cautious in megadosing any vitamin or mineral or amino acid.

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Last updated Apr 1, 2019

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