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Vitamin C

Other name(s):

anti-scorbutic agent, ascorbic acid, calcium ascorbate, dehydroascorbic acid, sodium ascorbate

General description

Vitamin C (ascorbic acid) is a water-soluble vitamin. It’s found in many fruits and vegetables. It is a popular supplement. Many people feel that large doses (megadoses) provide benefits for the body. Vitamin C is important in the development and maintenance of the connective tissues of the body. Vitamin C is also a potent antioxidant. Some studies show that vitamin C may help reduce the symptoms and duration of the common cold.

Vitamin C plays many roles in the chemistry of the human body. It’s needed for the production of collagen. This is a critical constituent of the body's connective tissue. It also helps increase the absorption of iron from the intestines. This is needed to make hemoglobin. This is the oxygen-carrying pigment inside of red blood cells.

The body uses vitamin C to make other important substances. These include carnitine, tyrosine, steroids made in the adrenal gland, and neurotransmitters (agents used in the conduction of nerve impulses). Vitamin C is needed for many chemical reactions. It’s involved in converting folic acid to its more active form, tetrahydrofolic acid. It also prevents its degradation into inactive metabolites that are no longer useful to the body.

Vitamin C is also a strong antioxidant. Antioxidants are thought to play a role in slowing the aging process, reducing damage to the lining of blood vessels, and reducing the risk of some types of cancer. Mounting evidence shows that vitamin C has a role in all of these processes.

Medically valid uses

Before the discovery of vitamin C, scurvy affected people who had little access to fresh fruits and vegetables. Scurvy was common among sailors who were away at sea for months at a time. When it was discovered that eating limes could prevent scurvy, British sailors were nicknamed "Limeys." Later, vitamin C was discovered. It was used to prevent and treat scurvy. Today, people take vitamin C supplements to make sure they get enough of the vitamin, even if their diet is poor.

Research suggests that vitamin C plays a role in decreasing the symptoms of the common cold. It may also reduce how long the cold lasts. Colds are the most common upper-respiratory infection. They account for the greatest number of missed workdays. The benefits of reducing the length of a cold, even by a day or two, with the use of vitamin C are great. While it can reduce symptoms and shorten a cold, vitamin C likely doesn’t prevent colds.

Unsubstantiated claims

Please note that this section reports on claims that have not yet been substantiated through studies.

Vitamin C is said to help prevent or cure gum disease (periodontitis). It may also prevent some cancers and protect the body against effects of pollution. It may also prevent blood clots and reduce bruising.

Recommended intake

Vitamin C is measured in milligrams (mg). Tablets and chewable tablets are the most common forms. It’s also available in time-release capsules, powder, lozenges, liquid, and injections. The RDA is the recommended dietary allowance. ULs is Tolerable Upper Intake Levels.

Group

RDA

ULs

Infants (0–6 months)

40 mg

n/a (infants should only take vitamin C in foods)

Infants (7–12 months)

50 mg

n/a (infants should only take vitamin C in foods)

Children (1–3 years)

15 mg

400 mg

Children (4–8 years)

25 mg

650 mg

Children (9–13 years)

45 mg

1,200 mg

Males (14–18 years)

75 mg

1,800 mg

Females (14–18 years)

65 mg

1,800 mg

Males (19 years and older)

90 mg

2,000 mg

Females (19 years and older)

75 mg

2,000 mg

Pregnancy (14–18 years)

80 mg

1,800 mg

Pregnancy (19 years and older)

85 mg

2,000 mg

Breastfeeding (14–18  years)

115 mg

1,800 mg

Breastfeeding (19 years and older)

120 mg

2,000 mg

 

People who smoke may need an extra 35 mg of Vitamin C per day.

Vitamin C taken by mouth or injection is effective for curing scurvy. In adults, taking 100–250 mg by mouth four times per day for one week is enough to improve symptoms and boost vitamin C stores. Some experts recommend 1–2 g per day for two days followed by 500 mg per day for one week. Symptoms should start to improve within 24–48 hours. You should be fully better within 7 days.  For asymptomatic vitamin C deficiency, you may need lower doses.

Vitamin C is sensitive to light and oxygen in the atmosphere. You should store supplements in light-resistant containers. Store them at room temperature or in the refrigerator. But do not freeze them. Don’t store them in metal containers.

Many fruits and vegetables supply vitamin C. The following table represents a sample of sources.

Food source

Nutrient content per 100 grams

Parsley

172 mg

Black currants

136 mg

Peppers

128 mg

Horseradishes

120 mg

Broccoli

113 mg

Brussels sprouts

100 mg

Cauliflower

78 mg

Strawberries

60 mg

Spinach

51 mg

Oranges

50 mg

Vitamin C is the most easily changed nutrient. It’s readily changed or broken down in handling, storing, or cooking. Fresh produce yields the highest levels of vitamin C. If vegetables are wilted or withered, the vitamin C levels will be significantly reduced. Fresh potatoes have a high vitamin C content. But winter storage reduces the level to only a fifth of the original content. Boiling reduces it even further.

High temperatures quicken the breakdown of vitamin C in the presence of oxygen or light. Cooking fruits and vegetables destroys much of the vitamin C activity. You should eat raw or lightly cooked fruits and vegetables to get the highest amount of vitamin C.

You may need vitamin C supplements if you have an inadequate diet with insufficient fresh fruits and vegetables. Or you may need them if you drink moderate to heavy amounts of alcohol or illegal drugs.

You may also need vitamin C supplements if you’re continually exposed to cold climates. This includes people who work outdoors or do strenuous physical activity outside in very cold weather. Emotional or physical stress and prolonged illness or major surgery also increases the need for this vitamin.

People who have hyperactive thyroid gland (thyrotoxicosis), insufficient stomach acid (achlorhydria), or have had removal of part or all of the stomach (gastrectomy) may need more vitamin C.

Women who are pregnant or breastfeeding may need to take supplements, but you should talk to your healthcare provider before doing so.

Vitamin C deficiency can lead to scurvy. Scurvy is marked by increased bleeding, especially of the gums, skin, muscles, and internal organs.

Other symptoms of vitamin C deficiency include slow healing of wounds, rough fissured skin, changes in the bones, and joint pain and fluid in the joints. They also include enlargement of the hair follicles, with a build-up of skin at the base of the hair. Vitamin C deficiency may also cause anemia and fatigue.

Side effects, toxicity, and interactions

There are no side effects linked with reasonable doses of vitamin C. Excess vitamin C comes out in the urine. Side effects from too much vitamin C may include the following:

  • Stomach pain or cramping

  • Nausea or vomiting

  • Diarrhea

  • Urinating more than normal

  • Blood in your urine

If you’re prone to kidney stones, high doses of vitamin C may aggravate kidney stones.

Some forms of vitamin C contain sulfites or tartrazine. Make sure your supplement doesn’t contain either of these chemicals if you’re allergic to them.

Medicine interactions

If you take any of the following medicines, you should talk to your healthcare provider before taking vitamin C supplements:

  • Acetaminophen or aluminum-containing antacids such as aluminum hydroxide. Vitamin C may increase the side effects of these medicines.

  • Aspirin. Vitamin C may cause aspirin to build up in your body, and aspirin may decrease the levels of vitamin C in your body.

  • Barbiturates. These include phenobarbital, pentobarbital, and secobarbital. Vitamin C may keep these medicines from working as well as they should.

  • Fluphenazine. Vitamin C may reduce the amount of this medicine in your body.

  • Indinavir. Vitamin C may reduce the amount of this medicine in your body.

  • Nicotine products, such as cigarettes, may decrease the effects of vitamin C.

  • Oral estrogens. These may decrease the effects of vitamin C in your body. Vitamin C may increase the levels of ethinyl estradiol in your body.

  • Tetracycline antibiotics. These include doxycycline, minocycline, and tetracycline may keep vitamin C from working as well as it should in your body.

  • Warfarin. Vitamin C may interfere with the blood-thinning effects of this medicine.

There is limited evidence that high-dose vitamin C may reduce side effects of levodopa. These include nausea or trouble with coordination.

High doses of vitamin C aren’t recommended in people with kidney failure. Talk to your healthcare provider before taking vitamin C supplements if you take medicines that may cause kidney problems.

Herbs and dietary supplements interactions

Vitamin C may increase the absorption of iron in your gastrointestinal tract. It may also increase the absorption of lutein vitamin supplements.

Large doses of vitamin C may interfere with the absorption and metabolism of vitamin B12.

In theory, large doses of vitamin C may interact with herbs and supplements that have hormonal, antibacterial, and blood-thinning (anticoagulant) activity.