Vitamin C (ascorbic acid) is a nutrient your body needs to form blood vessels, cartilage, muscle, and collagen in bones. Vitamin C is also vital to your body’s healing process.
Vitamin C is an antioxidant that helps protect your cells against the effects of free radicals — molecules produced when your body breaks down food or is exposed to tobacco smoke and radiation from the sun, X-rays, or other sources. Free radicals might play a role in heart disease, cancer, and other diseases. Vitamin C also helps your body absorb and store iron.
Because your body doesn’t produce vitamin C, you need to get it from your diet. Vitamin C is found in citrus fruits, berries, potatoes, tomatoes, peppers, cabbage, Brussels sprouts, broccoli, and spinach. Vitamin C is also available as an oral supplement, typically in the form of capsules and chewable tablets.
The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). For adult males, the RDA is 90 mg daily. For females 19 years and older, the RDA is 75 mg daily. While pregnant and breastfeeding, the RDA is 120 mg daily for people 19-50 years old. In children, the RDA depends on age.
Vitamin C is also available in supplements, combination products, liquids, lotions, creams, serums, sprays, and patches. Supplements have been used safely by adults in doses up to 2000 mg daily. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.
When taken at appropriate doses, oral vitamin C supplements are generally considered safe. Taking too much vitamin C can cause side effects, including:
- Nausea, vomiting, and diarrhea
- Stomach cramps or bloating
- Fatigue and sleepiness, or sometimes insomnia
- Skin flushing
In some people, oral vitamin C supplements can cause kidney stones, especially when taken in high doses. Long-term use of oral vitamin C supplements over 2,000 milligrams a day increases the risk of significant side effects.
Tell your doctor that you’re taking vitamin C supplements before having any medical tests. High levels of vitamin C might interfere with the results of certain tests, such as stool tests for occult blood or glucose screening tests.
Possible interactions include:
- Aluminum. Taking vitamin C can increase your absorption of aluminum from medications containing aluminum, such as phosphate binders. This can be harmful for people with kidney problems.
- Chemotherapy. There is concern that use of antioxidants, such as vitamin C, during chemotherapy might reduce the effect of chemotherapy drugs.
- Estrogen. Taking vitamin C with oral contraceptives or hormone replacement therapy might increase your estrogen levels.
- Protease inhibitors. Oral use of vitamin C might reduce the effect of these antiviral drugs.
- Statins and niacin. When taken with vitamin C, the effects of niacin and statins, which might benefit people with high cholesterol, could be reduced.
- Warfarin (Jantoven). High doses of vitamin C might reduce your response to this anticoagulant.