Side Effects of Emergen-C

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Emergen-C is a dietary supplement that’s jam-packed with vitamin C, multiple B vitamins and small amounts of several minerals. Makers of Emergen-C claim that the combination of these nutrients can rev up your immune system, keeping you as healthy as possible and minimizing your risk of getting sick. Emergen-C hasn’t been proved a cure-all for illnesses, however. While it is generally safe if you’re in good overall health, it could cause a few side effects.

Gastrointestinal Complications

One dose of Emergen-C has 1,000 milligrams of vitamin C. While that’s more than 11 times the amount of vitamin C you need in a day, it’s still probably not dangerous, since your body flushes out any extra vitamin C when you urinate. It can be problematic if you take two doses in a single day though -- the recommendation is only one dose a day. Vitamin C has a tolerable upper intake level of 2,000 milligrams daily, set by the Food and Nutrition Board of the Institute of Medicine. Getting this much vitamin C, or more, is likely to give you a severe bellyache, diarrhea and nausea.

Possible Gluten Content

If you have celiac disease or a gluten sensitivity, Emergen-C is something you’ll need to avoid. The manufacturer doesn’t use any ingredients that directly contain gluten, like wheat flour. But the company also doesn’t certify that the ingredients they use come from gluten-free processing plants, nor does it test its final product for gluten. So while Emergen-C is probably gluten-free, it isn’t a promise. Any gluten particles in the supplement could cause diarrhea, constipation, fatigue, itchy skin or weight loss. These are all side effects of consuming gluten, if your body can’t process it.

Interactions With Medications

One dose of Emergen-C has about 420 percent of the daily recommendation of vitamin B-6 and 500 percent of the recommendation for vitamin B-12. Although higher doses of these vitamins are rarely toxic, they’re both known to interact poorly with certain medications. For example, vitamin B-6 affects the functions of certain antibiotics, anti-epileptic medications and drugs used to treat breathing disorders, such as asthma or emphysema. B-12 also has the potential to react poorly with certain drugs. Because of possible problems, go over all of the medications you take, including Emergen-C, with your doctor, just to be safe.

Allergic Reactions

While uncommon, it’s possible to be allergic to any of the ingredients in Emergen-C. If you’re mildly allergic, you may experience watery eyes, itching, hives or rashes. In serious allergic breakouts, you could have difficulty breathing, start wheezing, have an abnormal pulse or even pass out. These serious complications are signs of anaphylaxis. Whether your reaction is mild or severe, get medical attention right away because symptoms sometimes get worse. Drug allergies can be fatal in some cases.