Vitamin C
A water-soluble vitamin the body cannot make, needed to build collagen and for immune function. It improves iron absorption from plants; too little causes scurvy.
75 mg women
How much you need
The official Recommended Dietary Allowance for adults, per day:
| Age | Men | Women | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| 19–50 years | 90 mg | 75 mg | 85 mg | 120 mg |
| 51–70 years | 90 mg | 75 mg | — | — |
| Over 70 | 90 mg | 75 mg | — | — |
People who smoke need 35 mg a day more than these amounts, because smoking increases oxidative stress and lowers vitamin C levels. People regularly exposed to secondhand smoke should make sure they meet the recommended amount.
People aged 18 fall in the official 14–18 group — 75 mg a day for males and 65 mg for females, 80 mg in pregnancy and 115 mg when breastfeeding, plus 35 mg for people who smoke. Its upper limit is 1,800 mg. Pregnancy and breastfeeding change what you need — confirm yours with your midwife, obstetrician or doctor.
Upper limit
| Age | Men | Women | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| 19–50 years | 2,000 mg | 2,000 mg | 2,000 mg | 2,000 mg |
| 51–70 years | 2,000 mg | 2,000 mg | — | — |
| Over 70 | 2,000 mg | 2,000 mg | — | — |
The upper limit covers vitamin C from food and supplements combined. It is the most that is unlikely to cause harm, not a target; long-term intakes above it may increase the risk of adverse effects. It does not apply to people receiving vitamin C as medical treatment, who should be under a doctor's care.
What it does
Unlike most animals, humans cannot make vitamin C, so it must come from the diet [1]. It is needed to make collagen — an essential part of the connective tissue that plays a vital role in wound healing — as well as L-carnitine and some neurotransmitters, and it is involved in protein metabolism [1]. It is an important antioxidant that helps regenerate others, including vitamin E, plays an important role in immune function, and improves the absorption of nonheme iron, the form found in plant foods [1].
Forms
Supplements usually contain ascorbic acid, which is absorbed as well as the vitamin C naturally present in foods such as orange juice and broccoli [1]. Other forms include sodium and calcium ascorbate, ascorbic acid with bioflavonoids, and combination products such as Ester-C [1]. In one study, plasma levels and urinary excretion did not differ between ascorbic acid, Ester-C and ascorbic acid with bioflavonoids, and its authors concluded that simple ascorbic acid is the preferred source [1].
Where it comes from
- Red pepper, sweet, raw½ cup95 mg
- Orange juice¾ cup93 mg
- Orange1 medium70 mg
- Grapefruit juice¾ cup70 mg
- Kiwifruit1 medium64 mg
How these five were chosen: The five foods with the most vitamin C per serving in the NIH fact sheet's food table. Fortified foods are marked.
| Item | Percent of the adult daily amount (90 mg) |
|---|---|
| Red pepper, raw | 106% |
| Orange juice | 103% |
| Orange | 78% |
| Grapefruit juice | 78% |
| Kiwifruit | 71% |
Getting the most from it
About 70% to 90% of vitamin C is absorbed at intakes of 30 to 180 mg a day, but above 1 g a day absorption falls below 50%, and the excess is excreted in urine [1]. Cells appear to be saturated at about 100 mg a day, and above 200 mg blood levels rise only marginally [1]. Vitamin C dissolves in water and is destroyed by heat, so long storage and cooking reduce it; steaming or microwaving may lessen the losses, and many of the best sources are eaten raw [1].
In the United States
Most Americans get enough vitamin C: in 2001–2002 national survey data, average intake from food and drink was 105.2 mg a day for men and 83.6 mg for women, meeting the recommended amount for most nonsmoking adults [1]. In 1999–2000, about 35% of adults took a multivitamin, which typically contains vitamin C, and 12% took a separate vitamin C supplement [1]. Citrus fruits, tomatoes and tomato juice, and potatoes are major sources in the American diet, and five varied servings of fruit and vegetables a day can provide more than 200 mg [1].
Who is most likely to run low
- People who smoke, and people exposed to secondhand smoke — smoking lowers vitamin C levels in blood and white blood cells [1]
- People with limited food variety, including some older people on low incomes who cook for themselves, people who misuse alcohol or drugs, food faddists and people with mental illness [1]
- People with severe intestinal malabsorption or cachexia, some people with cancer, and people with end-stage kidney disease on hemodialysis [1]
What deficiency looks like
Deficiency causes scurvy, which can appear within a month of eating less than about 10 mg a day [1]. Early symptoms include fatigue, malaise and inflamed gums; as it progresses, weakened connective tissue causes small red or purple spots and bruising under the skin, joint pain, poor wound healing, thickened skin and corkscrew hairs, along with depression, swollen and bleeding gums, and loose or lost teeth [1]. Iron deficiency anemia can follow, and untreated, scurvy is fatal [1]. It is rare in developed countries but can still occur in people with very limited diets [1].
What the evidence supports, and what it doesn't
Established. Vitamin C prevents and cures scurvy; in the mid-1700s, James Lind showed that citrus fruit cured it, although ascorbic acid was not proven to be the active component until 1932 [1]. The recommended amounts are based on vitamin C's functions in white blood cells and are much higher than the amount needed to prevent deficiency [1].
Not supported by trials. The common cold in the general population: a 2007 Cochrane review found that taking at least 200 mg a day did not reduce the risk of catching a cold, and taking it after symptoms began did not shorten colds or ease symptoms [1]. Cancer prevention: most trials, usually of vitamin C with other nutrients, found no effect — in the Physicians' Health Study II, 500 mg a day with vitamin E every other day for a mean of 8 years did not reduce prostate or total cancer [1]. Heart disease: in the Women's Antioxidant Cardiovascular Study, 8,171 women aged 40 and older with a history of cardiovascular disease took 500 mg a day for a mean of 9.4 years with no overall effect on cardiovascular events, and 500 mg a day had no effect on major cardiovascular events in the Physicians' Health Study II [1]. Cataracts: in AREDS, 500 mg of vitamin C with vitamin E and beta-carotene for an average of 6.3 years did not lower the risk of cataracts [1].
Mixed. The common cold under physical stress: in trials of marathon runners, skiers and soldiers exposed to extreme exercise or cold, 250 mg to 1 g a day halved the number of colds, and in the general population regular vitamin C shortened colds modestly — by 8% in adults and 14% in children [1]. Age-related macular degeneration: vitamin C has not been shown to prevent AMD, but in AREDS, people at high risk of advanced AMD who took 500 mg of vitamin C with vitamin E, beta-carotene, zinc and copper had a 28% lower risk of progressing to it over an average of 6.3 years [1]. Diet and disease: observational studies link diets high in vitamin C, fruit and vegetables with lower risks of several cancers and of heart disease, but the results of prospective studies are inconsistent, and many trials may have started with people whose vitamin C levels were already near saturation [1].
Too much
Vitamin C has low toxicity and is not believed to cause serious harm at high intakes [1]. The most common complaints are diarrhea, nausea, abdominal cramps and other digestive upsets, from unabsorbed vitamin C in the gut [1]. High intakes could raise oxalate and uric acid in urine and contribute to kidney stones, although studies conflict; the best evidence is in people with pre-existing hyperoxaluria [1]. Because vitamin C increases iron absorption, chronic high doses could worsen iron overload in people with hereditary hemochromatosis [1].
Medicines that interact
The safety of vitamin C and other antioxidants during cancer treatment is controversial: some data suggest they might protect tumour cells from radiation and chemotherapy drugs, and people having chemotherapy or radiation should consult their oncologist before taking vitamin C or other antioxidant supplements, especially in high doses [1]. Vitamin C combined with other antioxidants may blunt the rise in HDL cholesterol from combined niacin and simvastatin (Zocor) therapy, and health care providers should monitor lipid levels in people taking both statins and antioxidant supplements [1]. If you take any of these regularly, talk to your doctor or pharmacist before taking a vitamin C supplement.
References
- NIH Office of Dietary Supplements. Vitamin C — Fact Sheet for Health Professionals. Updated 31 July 2025. ods.od.nih.gov
How we reviewed this page
Every value on this page comes from the NIH Office of Dietary Supplements — Vitamin C, Health Professional Fact Sheet, which presents the official U.S. intake recommendations set by the National Academies. The source was last updated on July 31, 2025, and this page was checked against it on October 18, 2026. Numbered markers link to the source for each claim, so you can check the original rather than take our word for it.
Drafted with AI assistance, then edited and fact-checked by a human. No value is published on the strength of a model's recall.
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General information only. This is not medical advice.