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Vitamin C is an essential vitamin that must be consumed in the diet. Good sources include fresh fruits and vegetables, especially citrus fruits.

Vitamin C is needed for the body to develop and function properly. It plays an important role in immune function. Most experts recommend getting vitamin C from the diet rather than taking supplements. Fresh oranges and fresh-squeezed orange juice are good sources.

Historically, vitamin C was used for preventing and treating scurvy. Today, people most commonly use vitamin C for preventing and treating the common cold. It's also used for autism, breast cancer, heart disease and many other conditions, but there is no good scientific evidence to support many of these uses. There is also no good evidence to support using vitamin C for COVID-19.

Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
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When taken by mouth: Vitamin C is likely safe for most people. In some people, vitamin C might cause side effects such as stomach cramps, nausea, heartburn, and headache. The chance of getting these side effects increases with higher doses. Taking more than 2000 mg daily is possibly unsafe and may cause kidney stones and severe diarrhea. In people who have had a kidney stone, taking amounts greater than 1000 mg daily increases the risk of getting more kidney stones.

When applied to the skin: Vitamin C is likely safe for most people.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Vitamin C is likely safe to take by mouth during pregnancy in amounts no greater than 2000 mg daily for those 19 years and older and 1800 mg daily for those 14-18 years old. Taking too much vitamin C during pregnancy can cause problems for the newborn baby. Vitamin C is possibly unsafe when taken by mouth in excessive amounts.

Infants and children: Vitamin C is likely safe when taken by mouth appropriately. Vitamin C is possibly unsafe when taken by mouth in amounts higher than 400 mg daily for children 1-3 years, 650 mg daily for children 4-8 years, 1200 mg daily for children 9-13 years, and 1800 mg daily for adolescents 14-18 years.

Alcohol use disorder: People who regularly use alcohol, especially those who have other illnesses, often have vitamin C deficiency. These people might need to be treated for a longer time than normal to restore vitamin C levels to normal.

Cancer: Cancerous cells collect high concentrations of vitamin C. Until more is known, only use high doses of vitamin C under the direction of your oncologist.

Chronic kidney disease: Long-term kidney disease might increase the risk of vitamin C deficiency. Vitamin C supplements might also increase the amount of oxalate in the urine in some people. Too much oxalate in the urine can increase the risk of kidney failure in people with kidney disease.

A metabolic deficiency called "glucose-6-phosphate dehydrogenase" (G6PD) deficiency: Large amounts of vitamin C can cause red blood cells to break in people with this condition. Avoid excessive amounts of vitamin C.

Kidney stones: Large amounts of vitamin C can increase the chance of getting kidney stones. Do not take vitamin C in amounts greater than those found in basic multivitamins.

Smoking and chewing tobacco: Smoking and chewing tobacco lowers vitamin C levels. People who smoke or chew tobacco should consume more vitamin C in the diet.

Acetaminophen (Tylenol, others)

Interaction Rating=Minor Be watchful with this combination.

The body breaks down acetaminophen (Tylenol, others) to get rid of it. Large amounts of vitamin C can decrease how quickly the body breaks down acetaminophen. It is not clear exactly when or if this interaction is a big concern.

Aluminum

Interaction Rating=Moderate Be cautious with this combination.

Aluminum is found in most antacids. Vitamin C can increase how much aluminum the body absorbs. But it isn't clear if this interaction is a big concern. Take vitamin C two hours before or four hours after antacids.

Aspirin

Interaction Rating=Minor Be watchful with this combination.

The body breaks down aspirin to get rid of it. Large amounts of vitamin C might decrease the breakdown of aspirin. Decreasing the breakdown of aspirin might increase the effects and side effects of aspirin. Do not take large amounts of vitamin C if you take large amounts of aspirin.

Choline Magnesium Trisalicylate (Trilisate)

Interaction Rating=Minor Be watchful with this combination.

Vitamin C might decrease how quickly the body gets rid of choline magnesium trisalicylate (Trilisate). But it is not clear if this interaction is a big concern.

Estrogens

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down estrogens to get rid of them. Vitamin C might decrease how quickly the body gets rid of estrogens. Taking vitamin C along with estrogens might increase the effects and side effects of estrogens.

Fluphenazine (Prolixin)

Interaction Rating=Moderate Be cautious with this combination.

Large amounts of vitamin C might decrease how much fluphenazine (Prolixin) is in the body. Taking vitamin C along with fluphenazine (Prolixin) might decrease the effectiveness of fluphenazine (Prolixin).

Medications for cancer (Chemotherapy)

Interaction Rating=Moderate Be cautious with this combination.

Vitamin C is an antioxidant. There is some concern that antioxidants might decrease the effectiveness of some medications used for cancers. But it is too soon to know if this interaction occurs.

Medications used for HIV/AIDS (Protease Inhibitors)

Interaction Rating=Moderate Be cautious with this combination.

Taking large doses of vitamin C might reduce how much of some medications used for HIV/AIDS stays in the body. This could decrease the effectiveness of some medications used for HIV/AIDS.
Some of these medications used for HIV/AIDS include amprenavir (Agenerase), nelfinavir (Viracept), ritonavir (Norvir), and saquinavir (Fortovase, Invirase).

Medications used for lowering cholesterol (Statins)

Interaction Rating=Moderate Be cautious with this combination.

Taking vitamin C, beta-carotene, selenium, and vitamin E together might decrease the effectiveness of some medications used for lowering cholesterol. It is not known if vitamin C alone decreases the effectiveness of some medications used for lowering cholesterol.Some medications used for lowering cholesterol include atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Mevacor), and pravastatin (Pravachol).

Niacin

Interaction Rating=Moderate Be cautious with this combination.

Taking vitamin C along with vitamin E, beta-carotene, and selenium might decrease some of the helpful effects of niacin. Niacin can increase the good cholesterol. Taking vitamin C along with these other vitamins might decrease the effectiveness of niacin for increasing good cholesterol.

Nicardipine (Cardene)

Interaction Rating=Minor Be watchful with this combination.

Vitamin C is taken up by cells. Taking nicardipine (Cardene) along with vitamin C might decrease how much vitamin C is taken in by cells. The significance of this interaction is not clear.

Nifedipine

Interaction Rating=Minor Be watchful with this combination.

Vitamin C is taken up by cells. Taking nifedipine (Adalat, Procardia) along with vitamin C might decrease how much vitamin C is taken in by cells. The significance of this interaction is not clear.

Salsalate (Disalcid)

Interaction Rating=Minor Be watchful with this combination.

Vitamin C might decrease how quickly the body gets rid of salsalate (Disalcid). Taking vitamin C along with salsalate (Disalcid) might cause too much salsalate (Disalcid) in the body, and increase the effects and side effects of salsalate.

Warfarin (Coumadin)

Interaction Rating=Moderate Be cautious with this combination.

Warfarin (Coumadin) is used to slow blood clotting. Large amounts of vitamin C might decrease the effectiveness of warfarin (Coumadin). Decreasing the effectiveness of warfarin (Coumadin) might increase the risk of clotting. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.

Acerola: Acerola contains high levels of vitamin C. Don't take large amounts of acerola along with vitamin C. This might give you too much vitamin C. Adults should not take more than 2000 mg vitamin C per day.
Chromium: Vitamin C might increase chromium absorption. Don't take large doses of chromium and vitamin C together. It isn't known whether separating the doses by several hours avoids this interaction.
Copper: High doses of vitamin C (1500 mg daily) can decrease copper levels in the blood. This interaction probably isn't important except in people whose dietary intake of copper is low.
Grape: Taking vitamin C with grape seed might increase blood pressure in people with high blood pressure. It's not clear why this happens.
Iron: Vitamin C increases the absorption of iron when taken at the same time. But taking a vitamin C supplement to improve absorption of iron from the diet or from supplements probably isn't necessary for most people.
Rose hip: Rose hip contains high levels of vitamin C. Don't take large amounts of rose hip along with vitamin C. This might give you too much vitamin C. Adults should not take more than 2000 mg vitamin C per day.
Vitamin B12: There have been concerns that vitamin C can lower vitamin B12 levels in the body. But vitamin C supplements don't seem to affect levels of vitamin B12.

There are no known interactions with foods.

Vitamin C is an important nutrient. Fresh fruits and vegetables, especially citrus fruits, are good sources of vitamin C. 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, 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.

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