Vitamins
Vitamin C
Vitamin C is an essential, water-soluble vitamin that you need to obtain through your diet. Its principal chemical form is L-ascorbic acid.
Your body cannot make vitamin C, so you obtain it from food, particularly fruit and vegetables. It is a micronutrient, rather than a food in its own right. The nutritional term covers both L-ascorbic acid and its oxidised form, dehydroascorbic acid, which also has vitamin C activity. Vitamin C can be added to foods and supplements. When ascorbic acid is used as a food additive, it is identified as E 300.
Vitamin C: an essential micronutrient
Vitamin C is a water-soluble vitamin that your body cannot make. You therefore need to obtain it through your diet. The term covers L-ascorbic acid and its oxidised form, dehydroascorbic acid, which also has vitamin C activity.
What does vitamin C do?
Vitamin C contributes to many normal body functions. The functions below are described by authorised EU health claims in Regulation (EU) No 432/2012. To use these claims, a food must meet at least the conditions for a source of vitamin C.
- It contributes to normal collagen formation for the normal function of bones, cartilage, skin, blood vessels, gums and teeth.
- It contributes to normal energy-yielding metabolism, nervous system function, psychological function and immune system function.
- It contributes to the protection of cells from oxidative stress and to the regeneration of the reduced form of vitamin E.
- It increases iron absorption, particularly the absorption of non-haem iron from plant foods.
- It contributes to the reduction of tiredness and fatigue.
These claims describe nutrient functions. They do not mean that extra high doses enhance immunity beyond normal function or prevent infections when intake is already adequate. Fatigue also has many possible causes and is not necessarily relieved by more vitamin C.
Vitamin C in your diet
Fruit, vegetables, their juices and potatoes contribute substantially to vitamin C intake in European diets. The amount varies with the food, storage and preparation. Prolonged storage and cooking can reduce it because vitamin C is water-soluble and heat-sensitive. Steaming or microwaving may reduce losses during preparation.
More is not automatically better
As intake rises, the fraction of vitamin C absorbed decreases and blood concentrations approach a plateau. A higher dose therefore does not automatically provide a proportionally greater benefit. Ordinary ascorbic acid in supplements has comparable bioavailability to naturally occurring ascorbic acid in foods. A general advantage of special formulations is not adequately established. This does not make a supplement nutritionally equivalent to a whole food.
Studies suggest that vitamin C supplements may slightly lower systolic blood pressure in the short term. Sustained benefit is not established. In adults with type 2 diabetes, there are indications of a reduction in HbA1c, but the certainty of the evidence is very low. These findings do not justify replacing blood-pressure or diabetes treatment.
How nutrition works
Bone health
Dental health
Energy metabolism
Nervous system
Psychological function
Vitamin C contributes to normal psychological function. [2]
Immune system
Tiredness and fatigue
Vitamin C contributes to the reduction of tiredness and fatigue. [2]
Blood pressure
Glycaemic control
Collagen formation
Skin, hair and nails
Protection from oxidative stress
Iron absorption
Common cold
Regular vitamin C supplementation does not meaningfully reduce the risk of catching a cold in the general population. [5]
Cardiovascular health
Vitamin C supplements have no demonstrated benefit for preventing major cardiovascular events. [6]
Statements & evidence
Vitamin C contributes to maintain the normal function of the immune system during and after intense physical exercise [2]
This claim may only be used for food providing 200 mg of vitamin C daily. Consumers must be informed that the beneficial effect is obtained with 200 mg daily in addition to the recommended daily intake. This is a condition of the claim, not a general recommendation to take supplements.
Vitamin C contributes to normal collagen formation for the normal function of cartilage [2]
The food must meet at least the conditions for a source of vitamin C. The claim does not mean that additional supplements repair cartilage damage.
Vitamin C contributes to the protection of cells from oxidative stress [2]
The food must meet at least the conditions for a source of vitamin C. This antioxidant function does not establish general disease protection from high-dose supplements.
Vitamin C contributes to the regeneration of the reduced form of vitamin E [2]
The food must meet at least the conditions for a source of vitamin C. The claim describes an interaction between the vitamins, not a recommendation to supplement both.
Vitamin C increases iron absorption [2][7]
The food must meet at least the conditions for a source of vitamin C. The effect particularly concerns non-haem iron, such as that in plant foods. The claim is not a promise to treat iron deficiency.
Vitamin C is a water-soluble vitamin. Humans cannot make it and must obtain it through their diet. [7]
Vitamin C is also known as L-ascorbic acid. Being water-soluble does not mean that unlimited amounts are harmless.
Fruit, vegetables, their juices and potatoes are major contributors to vitamin C intake in European diets. [8][7]
This describes their contribution to dietary intake, not a uniform vitamin C content. Content varies with the food, storage and preparation.
Prolonged storage and cooking can reduce the vitamin C content of foods. [7]
Vitamin C is water-soluble and heat-sensitive. Steaming or microwaving may reduce cooking losses; the size of the loss depends on preparation.
Vitamin C absorption and blood concentrations do not increase proportionally as intake rises. [8][7]
At higher intakes, the fraction absorbed decreases and blood concentrations progressively approach a plateau. A higher dose therefore does not automatically mean a proportionally greater benefit.
The ascorbic acid commonly used in supplements has comparable bioavailability to naturally occurring ascorbic acid in foods. [7]
Bioavailability describes how well the body can absorb and use a substance. Comparable bioavailability does not make a supplement nutritionally equivalent to a whole food.
EFSA sets population reference intakes for healthy adults of 110 mg of vitamin C per day for men and 95 mg per day for women. [8]
These values refer to total intake, not supplement doses. EFSA proposes an additional 10 mg per day during pregnancy and an additional 60 mg per day during exclusive breastfeeding in the first six months. Reference values are not individual prescriptions.
High vitamin C intakes can cause diarrhoea, abdominal distension and cramps. [9]
Tolerance varies between individuals. Being water-soluble does not automatically make very high doses safe.
EFSA could not establish a tolerable upper intake level for vitamin C because the evidence was insufficient. [9]
The evidence gap concerns setting a reliable upper limit. It does not mean that unlimited amounts are safe.
A general bioavailability advantage of alternative vitamin C formulations over ordinary ascorbic acid is not adequately established. [7]
The NIH summary describes few human comparisons and no consistent advantages. This establishes neither superiority of all alternative forms nor complete equivalence between them.
Safety information
Upper level · Adults
US adult upper intake level: 2,000 mg daily
The US upper intake level for people aged 19 and over is 2,000 mg vitamin C daily from food, drinks and supplements combined, including during pregnancy and breastfeeding. It is not a recommended intake or a guarantee of safety for people with underlying conditions. [7]
Upper level · Children and adolescents (1–17 years)
US upper intake levels depend on age
US daily total-intake upper levels are 400 mg at ages 1–3, 650 mg at 4–8, 1,200 mg at 9–13 and 1,800 mg at 14–18. The last limit also applies during pregnancy and breastfeeding at those ages. No upper level is established for infants under 12 months because evidence is insufficient, not because high doses are known to be safe. [7]
Upper level
BfR proposed maximum for supplements
BfR proposes a maximum of 250 mg vitamin C per recommended daily dose of a food supplement. This is a product-level recommendation, not an upper limit for total dietary intake or a binding legal maximum. [12]
Side effect
High oral doses can upset the gut
Vitamin C has low toxicity at ordinary food intakes. High oral doses can cause diarrhoea, nausea and abdominal cramps. These symptoms usually settle after stopping the supplement. [7]
Caution · Adult men
Possible association with kidney stones in men
A systematic review found an association between vitamin C supplements and kidney stones in men, but not in women. The limited evidence does not prove causation or provide a reliable safe-dose threshold. If you have previously had oxalate stones, avoid high-dose supplements without clinical advice. [13][14]
Caution
Seek clinical advice on high doses with kidney disease
If you have impaired kidney function, receive dialysis or have a history of oxalate stones, do not use high-dose vitamin C without clinical supervision. Oxalate-related kidney injury has been reported with high-dose use, especially prolonged intravenous administration. This is not a blanket warning against vitamin C in foods. [14]
Caution
Caution with iron overload
If you have haemochromatosis or another iron-overload disorder, discuss vitamin C supplements with your clinician. Vitamin C increases non-haem iron absorption; high doses can worsen iron overload and tissue damage in these conditions. [7]
Caution
G6PD deficiency: particular caution with infusions
In people with G6PD deficiency, vitamin C, particularly high intravenous doses, can cause severe red-cell breakdown. Tell the treatment team before an infusion; dosing and monitoring need specific assessment. This does not imply a general restriction on vitamin-C-containing foods. [14]
Side effect
Infusions have distinct adverse effects
Intravenous vitamin C can cause pain and swelling at the infusion site. Rapid administration can cause faintness, nausea, flushing, dizziness or headache. These risks should not be equated with vitamin C intake from food. [14]
Caution
High doses can distort test results
Tell your clinical team and laboratory about high-dose vitamin C, especially infusions. It can distort readings from some glucose meters and laboratory tests; some faecal occult-blood tests can give false-negative results. The effect depends on the assay and route of administration. [14][15]
Interaction
Deferoxamine: specialist supervision for supplements
If you receive deferoxamine, also called desferrioxamine, use vitamin C supplements only under specialist direction. Vitamin C can increase iron mobilisation but can also worsen tissue iron toxicity, including serious cardiac problems. [16]
Interaction
Deferiprone: possible interaction insufficiently studied
If you take deferiprone, discuss vitamin C supplements with your treatment team. Concurrent use has not been formally studied; EMA advises caution because of the known problems with deferoxamine. This does not directly establish a harmful interaction with deferiprone. [17]
Interaction
Discuss supplements during cancer treatment
During chemotherapy or radiotherapy, use vitamin C supplements, particularly high doses, only with your oncology team’s approval. Evidence on possible changes to treatment effects is mixed; clinically relevant harm from oral vitamin C is not conclusively established. This is not a blanket warning against fruit and vegetables. [7]
Interaction
Limited evidence for simvastatin plus niacin
A combination of vitamin C and other antioxidants attenuated the HDL increase with simvastatin plus niacin in a study. This does not establish an interaction with vitamin C alone or with all statins. If you receive this medicine combination, discuss antioxidant supplements with your treatment team. [7]
Interaction
Warfarin: interaction not reliably established
Some case reports suggest reduced warfarin activity with vitamin C, but small studies did not confirm this. A predictable interaction is not established. If you take warfarin, report substantial changes in supplement use and continue your usual INR monitoring. [14]
Interaction
Vitamin C may change levothyroxine absorption
Vitamin C taken at the same time may increase levothyroxine absorption. If you take levothyroxine, discuss starting or stopping a concurrently used vitamin C supplement with the clinician managing your treatment. Do not adjust your thyroid medicine yourself. [15]
Frequently asked questions
How much vitamin C do I need each day?
EFSA sets daily population reference intakes of 110 mg for healthy adult men and 95 mg for healthy adult women. These values refer to total intake, not supplement doses; reference intakes are higher during pregnancy and breastfeeding.
Which foods provide vitamin C?
Fruit and vegetables provide vitamin C; their juices and potatoes also contribute substantially to intake in European diets. The amount varies between foods and can decrease with prolonged storage and cooking.
Does vitamin C boost my immune system?
Vitamin C contributes to normal immune system function. This does not mean that extra high doses enhance immunity beyond normal function or prevent infections.
Are special vitamin C formulations better than ordinary ascorbic acid?
A general advantage of alternative formulations in absorption and availability to the body is not adequately established. Ordinary ascorbic acid in supplements has comparable bioavailability to naturally occurring ascorbic acid in foods.
Can I take too much vitamin C?
Yes: high oral doses can cause diarrhoea, nausea and abdominal cramps. EFSA has not established a tolerable upper intake level because evidence is insufficient—not because unlimited doses are safe. If you have kidney disease or iron overload, seek clinical advice before using high-dose supplements.
More entries
Folate
Folate is a water-soluble B vitamin. Its active forms take part in DNA synthesis and amino-acid metabolism.
Vitamin A
Vitamin A is an essential, fat-soluble vitamin. Your diet supplies it as preformed vitamin A or as precursors from plant foods.
Vitamin B12
Vitamin B12 is an essential, water-soluble vitamin. Your body needs it for normal nervous-system function, red blood cell formation and DNA synthesis.
Vitamin D
Vitamin D is a fat-soluble vitamin. The term mainly covers vitamins D₂ and D₃; your body can produce D₃ in the skin through exposure to UVB radiation.
Vitamin K
Vitamin K is an essential, fat-soluble vitamin. Your body needs it to activate proteins involved in blood clotting and bone metabolism.
Vitamin B6
Vitamin B6 is a water-soluble vitamin. Its active forms support many metabolic processes, particularly amino-acid metabolism.
Sources
- 01EFSA Journal · 2009Scientific Opinion on the substantiation of health claims related to vitamin C and protection of DNA, proteins and lipids from oxidative damage (ID 129, 138, 143, 148), antioxidant function of lutein (ID 146), maintenance of vision (ID 141, 142), collagen formation (ID 130, 131, 136, 137, 149), function of the nervous system (ID 133), function of the immune system (ID 134), function of the immune system during and after extreme physical exercise (ID 144), non-haem iron absorption (ID 132, 147), energy-yielding metabolism (ID 135), and relief in case of irritation in the upper respiratory tract (ID 1714, 1715) pursuant to Article 13(1) of Regulation (EC) No 1924/2006DOI 10.2903/j.efsa.2009.1226
- 02European Commission · 2012Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods, other than those referring to the reduction of disease risk and to children's development and healthOpen source
- 032023Vitamin C supplementation showed greater effects on systolic blood pressure in hypertensive and diabetic patients: an updated systematic review and meta-analysis of randomised clinical trialsPubMed 37791386Open source
- 04Diabetes Care · 2021Effects of Vitamin C Supplementation on Glycemic Control and Cardiovascular Risk Factors in People With Type 2 Diabetes: A GRADE-Assessed Systematic Review and Meta-analysis of Randomized Controlled TrialsOpen source
- 05Cochrane Database of Systematic Reviews · 2013Vitamin C for preventing and treating the common coldOpen source
- 06Cochrane Database of Systematic Reviews · 2017Vitamin C supplementation to prevent cardiovascular diseaseOpen source
- 07National Institutes of Health, Office of Dietary SupplementsVitamin C - Health Professional Fact SheetOpen source
- 08European Food Safety Authority · 2017Dietary Reference Values for nutrients: Summary reportOpen source
- 09Scientific Committee on Food; EFSA Scientific Panel on Dietetic Products, Nutrition and Allergies · 2006Tolerable Upper Intake Levels for Vitamins and MineralsOpen source
- 10European Parliament and Council of the European Union · 2011Regulation (EU) No 1169/2011 on the provision of food information to consumersOpen source
- 11European Food Safety AuthoritySummary tables of tolerable upper intake levels for vitamins and minerals, version 8Open source
- 12German Federal Institute for Risk AssessmentVitamin C is not only found in fruit and vegetablesOpen source
- 13Ascorbic Acid Supplements and Kidney Stones Incidence Among Men and Women: A systematic review and meta-analysisPubMed 30178451Open source
- 14DailyMed, US National Library of MedicineDailyMed - ASCOR- ascorbic acid injectionOpen source
- 15National Institutes of Health, Office of Dietary SupplementsDietary Supplements for Immune Function and Infectious Diseases - Health Professional Fact SheetOpen source
- 16Australian Commission on Safety and Quality in Health CareDBL Desferrioxamine Mesylate for Injection BPOpen source
- 17European Medicines AgencyFerriprox, INN-deferiprone: product informationOpen source
- 18European Commission · 2012Commission Regulation (EU) No 231/2012 laying down specifications for food additives listed in Annexes II and III to Regulation (EC) No 1333/2008Open source
- 192015Effect of vitamin C and vitamin E supplementation on endothelial function: a systematic review and meta-analysis of randomised controlled trialsPubMed 25919436Open source
- 20Efficacy of vitamin C with Fe supplementation in patients with iron deficiency anemia: a systematic review and meta-analysisOpen source
- 212019Limited evidence for a beneficial effect of vitamin C supplementation on biomarkers of cardiovascular diseases: an umbrella review of systematic reviews and meta-analysesPubMed 30683434Open source
- 22European Food Safety Authority · 2024Summary report on tolerable upper intake levels for vitamins and mineralsOpen source
- 23U.S. Preventive Services Task ForceVitamin and Mineral Supplements for the Primary Prevention of Cardiovascular Disease and Cancer: A Systematic Evidence Review for the U.S. Preventive Services Task ForceOpen source
- 24Bundesinstitut für Risikobewertung (BfR)Vitamin C steckt nicht nur in Obst und GemüseOpen source
- 25Cochrane Database of Systematic ReviewsVitamin C supplementation for prevention and treatment of pneumoniaOpen source