Vitamin C: what it does, how much you need, and how much is too much
By Vita · fact-checked against NIH ODS
Vita is Vitaminico's AI nutrition coach. Every number here is checked against the NIH Office of Dietary Supplements; these pages have not yet been reviewed by our registered dietitians.
Water-soluble vitamin that builds collagen and supports your immune system.
Vitamin C: key facts
- Everyday need (RDA/AI)
- 90 mg for men, 75 mg for women; people who smoke need an extra 35 mg/day
- Safe upper limit (UL)
- 2,000 mg
- Measured in
- mg
- Best foods
- Citrus fruits, red and green peppers, kiwifruit, broccoli, strawberries
Adult values from the NIH ODS Vitamin C fact sheet. Needs differ in pregnancy, lactation and childhood.
What does vitamin c do?
Vitamin C (L-ascorbic acid) helps your body make collagen, the protein that holds skin, blood vessels, and connective tissue together and is essential for wound healing. It also works as an antioxidant, supports normal immune function, and greatly improves the absorption of nonheme iron from plant foods. Because humans can't make vitamin C on their own and store little of it, you need a steady supply from food.
Why you might be low on vitamin c
- Smoking or regular exposure to secondhand smoke, which lowers vitamin C levels (smokers need 35 mg more per day)
- Eating a limited variety of foods with few fruits and vegetables
- Heavy alcohol or drug use, or restrictive/faddist diets
- Malabsorption or certain chronic diseases (severe intestinal malabsorption, cancer-related wasting, or end-stage kidney disease on dialysis)
- Infants fed boiled or evaporated cow's milk instead of breastmilk or formula
Signs of low vitamin c
These are common signals, not a diagnosis — a blood test and your clinician confirm a real gap.
- Fatigue and general malaise
- Swollen, bleeding, or inflamed gums and loose or lost teeth
- Easy bruising and tiny red spots under the skin (petechiae)
- Slow or poor wound healing
- Joint pain
- Rough, bumpy skin (hyperkeratosis) and corkscrew-shaped body hairs
Best food sources of vitamin c
| Food | Typical amount |
|---|---|
| Red bell pepper, sweet, raw | 95 mg per 1/2 cup |
| Orange juice | 93 mg per 3/4 cup |
| Orange | 70 mg per 1 medium fruit |
| Kiwifruit | 64 mg per 1 medium fruit |
| Broccoli, cooked | 51 mg per 1/2 cup |
| Strawberries, fresh, sliced | 49 mg per 1/2 cup |
| Brussels sprouts, cooked | 48 mg per 1/2 cup |
How much vitamin c is too much?
The tolerable upper intake level (UL) for adults is 2,000 mg per day. Intakes above the UL mainly cause diarrhea and GI upset; prolonged deficiency causes scurvy.
Vitamin C has low toxicity, but large doses above the adult upper limit of 2,000 mg per day can cause diarrhea, nausea, and abdominal cramps. Very high intakes may also raise kidney-stone risk in susceptible people and can worsen iron overload in those with hereditary hemochromatosis.
Stacking a multivitamin, a single supplement and fortified foods adds up faster than it looks — run your full dose through the free Supplement Safety Checker before adding anything new.
Vitamin C FAQ
Does vitamin C prevent or cure the common cold?
For most people, taking vitamin C regularly doesn't stop you from catching colds, though it may modestly shorten how long one lasts (about 8% in adults, 14% in children). Starting it only after symptoms appear hasn't been shown to help.
How much vitamin C do I need each day?
The RDA is 90 mg for adult men and 75 mg for adult women; people who smoke need an extra 35 mg per day. A single medium orange or half a cup of raw red pepper already covers a full day.
Should I take a supplement, or is food enough?
Most people can meet their needs from food -- five varied servings of fruits and vegetables provide more than 200 mg. If you do supplement, high doses can interact with chemotherapy, radiation, and some statin regimens, so check with your doctor first.
Source
Every RDA/AI, upper limit and unit on this page is drawn from the NIH Office of Dietary Supplements Vitamin C fact sheet ›.
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Educational, not medical advice. The upper limits shown are Tolerable Upper Intake Levels for healthy adults from all sources combined; needs differ in pregnancy, lactation, childhood and with some conditions or medications. This page does not diagnose a deficiency or set your dose — talk to your clinician before starting any high-dose supplement.