Vitamin C
Ascorbic acid
TL;DR
An essential water-soluble antioxidant required for collagen synthesis, immune cell function and iron absorption. Supplementation does not prevent colds in the general population but reliably shortens them by about 8-14%, and regular use halves cold incidence in people under heavy physical stress. Doses above 200 mg add little — absorption saturates and the rest is excreted.
Ideal For
- Low fruit and vegetable intake
- Smokers and regular secondhand smoke exposure
- Endurance athletes in heavy training blocks
- People taking iron supplements for deficiency
- Older adults with marginal diets
Avoid If
- History of calcium-oxalate kidney stones (doses above 1 g/day raise urinary oxalate)
- Haemochromatosis or iron overload (vitamin C increases iron absorption)
- G6PD deficiency at very high doses (haemolysis risk)
- Scheduled glucose-oxidase-based lab tests around high-dose use (assay interference)
Frequently Asked Questions
Does vitamin C prevent colds?
Is 1000 mg better than 200 mg?
Natural vs synthetic ascorbic acid?
Overview
Vitamin C (ascorbic acid) is a cofactor for the enzymes that hydroxylate collagen, synthesise carnitine and convert dopamine to noradrenaline, and it is the primary water-soluble antioxidant in plasma. Scurvy is rare, but intake below the RDA is common in low-fruit-and-vegetable diets. The trial record is clear on two points: routine supplementation does not stop the average person catching a cold, but it shortens colds by roughly half a day to a day, and in people under extreme physical stress (marathon runners, soldiers in cold conditions) it cuts cold incidence by around half. Megadoses are largely wasted: intestinal absorption falls steeply above 200 mg and excess is renally excreted.
How It Works
- Cofactor for prolyl and lysyl hydroxylase in collagen synthesis
- Regenerates vitamin E and neutralises reactive oxygen species in plasma and within leukocytes
- Required for carnitine synthesis and for dopamine beta-hydroxylase (noradrenaline production)
- Reduces ferric iron to the more absorbable ferrous form in the gut
- Supports neutrophil chemotaxis and microbial killing
Quick Facts
- Shortens colds by ~8% in adults and ~14% in children when taken regularly
- Halves cold incidence in people under extreme physical stress
- Does not prevent colds in the general population
- Absorption saturates above ~200 mg per dose — megadoses mostly exit in urine
- Enhances non-heme iron absorption 2-4 fold when taken together
- Smokers need ~35 mg/day more than non-smokers
Benefits & Outcomes
Flexibility Improvement
Necessary, not sufficient. Correct a deficiency and stop there.
Endothelial Function
Context-dependent. Correct a deficiency, but do not expect vascular benefit if your status is already good.
Cold Prevention
Vitamin C does not prevent colds in the general population but halves incidence in heavy exercisers and shortens colds ~8%.
Histamine Balance
Vitamin C enhances histamine degradation and modestly reduces histamine levels; a reasonable low-cost adjunct, not a standalone antihistamine.
Cerebral Blood Flow
Vitamin C supports endothelial function generally, with only indirect evidence for cerebral perfusion specifically.
Allergy Relief
Vitamin C has mild antihistamine properties; trials show small symptom reductions at higher doses.
Oxidative Damage Repair
Vitamin C corrects deficiency and supports plasma antioxidant capacity, but high doses around training blunt adaptation.
Sperm Quality
Vitamin C reduces seminal oxidative stress with inconsistent parameter effects.
UV Protection
Vitamin C is more useful applied topically than taken orally for photoprotection.
Ligament Health
Vitamin C is the essential cofactor for collagen synthesis — deficiency directly impairs ligament repair, and pairing with collagen pre-loading is evidence-based.
Hyperpigmentation Reduction
Topical vitamin C brightens pigmentation modestly; oral vitamin C does not.
Post-Exercise Soreness Reduction
High-dose vitamin C does not reliably reduce soreness and may interfere with training adaptation.
Reduced Oxidative Stress
Gram-level vitamin C around training blunts adaptation without delivering health benefits.
Respiratory Tract Protection
Regular vitamin C slightly shortens colds but does not prevent them in the general population.
Skin Elasticity
Vitamin C is genuinely required for collagen synthesis, and topical use has good photoageing data.
Telomere Protection
Vitamin C may reduce the oxidative stress that accelerates shortening, without outcome proof.
Tendon Strength
Vitamin C is a required cofactor for collagen cross-linking, making adequacy non-negotiable.
Venous Return
Vitamin C supports vessel wall collagen but does not treat venous insufficiency.
Wrinkle Reduction
Vitamin C matters for collagen synthesis but works better on skin than in a capsule.
Wound Healing
Vitamin C is essential for collagen formation; adequacy matters, megadoses do not.
Stress Hormone Regulation
Vitamin C is concentrated in the adrenals but supplementation evidence is old and thin.
Flu Prevention
Duration-reducer, not preventer — except for athletes in heavy training.
Immune Function
Vitamin C supports several arms of immune function and shortens colds modestly — a sensible baseline, not a shield.
Antioxidant Protection
Vitamin C is the body's primary water-soluble antioxidant and regenerates vitamin E — but supplementing above repletion does not improve health outcomes.
Collagen Production
Collagen synthesis is chemically impossible without vitamin C — it is a mandatory enzymatic cofactor, not an optional add-on.
Iron Absorption
Vitamin C substantially increases absorption of non-haem iron — the single most useful dietary trick for plant-based iron.
Skin Health Enhancement
Strong evidence for topical vitamin C on skin; oral vitamin C mainly matters for keeping collagen synthesis unconstrained.
Health Concerns Addressed
Varicocele
Vitamin C appears in antioxidant combination formulas studied for varicocele-related fertility problems, based on the oxidative-stress theory of sperm damage. Evidence is limited to combination trials; it does not treat the varicocele itself.
Dark Circles
Reasonable topical option for the pigmented type over months; irrelevant for hollows and shadows, and oral supplementation does nothing here.
Bruising Easily
Severe vitamin C deficiency (scurvy) genuinely causes easy bruising, and repletion fixes it dramatically — but true scurvy is rare, and supplementing when levels are normal does nothing for bruising.
Low-Grade Fever
Vitamin C does not treat fever or shorten most infections. Regular supplementation modestly shortens cold duration, but taking it once symptoms start has consistently failed to show benefit.
Varicose Veins
Vitamin C is marketed for varicose veins on the basis of its role in collagen synthesis and vessel integrity, but there is no meaningful trial evidence that it prevents or shrinks varicose veins.
Gout
A small urate-lowering effect and a modest prevention signal, but no meaningful benefit shown in established gout.
Cough
Modest evidence for shortening colds; none for chronic cough. An 8-week cough needs the big-three workup, not a vitamin.
Kidney Stones
Not a stone treatment; high-dose supplements are linked to more stones in men, so stone formers should avoid 1,000 mg a day or more.
Runny Nose
One of the best-studied supplements in medicine, and the answer is consistently no for the average person.
Chills
No role here. Treat the cause and use antipyretics for comfort if needed.
Frequent Sneezing
Lab antihistamine effects have not translated into reliable clinical benefit for allergic rhinitis.
Fever
Vitamin C does not treat fever or shorten illness once symptoms have started.
Frequent Infections
Regular vitamin C does not stop you catching colds, but it shortens them modestly — and it clearly helps people under heavy physical stress.
Acute Bronchitis
Regular vitamin C intake slightly shortens respiratory illness duration; starting it after symptoms begin does not reliably help.
Supporting Research73 studies
Scurvy: reemergence of nutritional deficiencies
Leger D
Perifollicular haemorrhage and easy bruising resolved within weeks of vitamin C repletion in patients with dietary deficiency.
Interventions for leg cramps in pregnancy
Luo L, et al
Across 8 trials (576 women), oral magnesium may reduce leg cramp frequency versus placebo in some trials but results were inconsistent; oral calcium showed no clear benefit; vitamin B complex and vitamin C evidence was very low certainty. No intervention was supported by high-quality evidence.
The impact of essential fatty acid, B vitamins, vitamin C, magnesium and zinc supplementation on stress levels in women: a systematic review
McCabe D, Lisy K
Magnesium, B vitamins and zinc showed modest improvements in perceived stress and mood-related irritability; effects were inconsistent across trials.
Effects of high-dose B vitamin complex with vitamin C and minerals on subjective mood and performance in healthy males
Kennedy DO, Veasey R, Watson A +4 more
Supplementation improved ratings of mental health and vigour, reduced subjective stress and mental fatigue, and improved performance on demanding multitasking.
Demonstration of rapid onset vascular endothelial dysfunction after hyperhomocysteinemia: an effect reversible with vitamin C therapy
Chambers JC, McGregor A, Jean-Marie J
Oral methionine loading raised homocysteine and acutely impaired flow-mediated endothelial function in healthy men.
Multivitamin use and telomere length in women
Xu Q, Parks CG, DeRoo LA +3 more
Daily multivitamin users had 5.1% longer telomeres on average, and higher dietary vitamin C and E intakes were associated with longer telomeres.
The effects of vitamin C supplementation on serum concentrations of uric acid: results of a randomized controlled trial
Huang HY, Appel LJ, Choi MJ +4 more
serum uric acid levels were significantly reduced in the vitamin C group
Effect of oral vitamin C supplementation on serum uric acid: a meta-analysis of randomized controlled trials
Juraschek SP, Miller ER, Gelber AC
the combined effect of these trials was a significant reduction in SUA
Effects of vitamin C supplementation on gout risk: results from the Physicians' Health Study II trial
Juraschek SP, Gaziano JM, Glynn RJ +4 more
The vitamin C assignment reduced new gout diagnoses by 12%
The Effect of Vitamin C Supplements on Urinary Stone Risk: A Systematic Review and Meta-Analysis
Farkouh A, Seibly E, Buell MI +4 more
Vitamin C supplements significantly increase urinary oxalate excretion in both SFs and NSFs
Ascorbic acid supplements and kidney stone incidence among men: a prospective study
Thomas LD, Elinder CG, Tiselius HG +2 more
dose-dependent 2-fold increased risk of kidney stone formation among men
Association between Oral vitamin C supplementation and serum uric acid: A meta-analysis of randomized controlled trials
Liu XX, Wang XX, Cui LL
vitamin C supplementation had a significant effect of lowering SUA
Effect of ascorbic acid consumption on urinary stone risk factors
Traxer O, Huet B, Poindexter J +2 more
We recommend limiting AA use to less than 2 gm daily in CaOx stone formers
Ascorbate increases human oxaluria and kidney stone risk
Massey LK, Liebman M, Kynast-Gales SA
increased urinary oxalate and TRI for calcium oxalate kidney stones in 40% of participants
Intake of vitamins B6 and C and the risk of kidney stones in women
Curhan GC, Willett WC, Speizer FE +1 more
Routine restriction of vitamin C to prevent stone formation appears unwarranted
Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up
Taylor EN, Stampfer MJ, Curhan GC
total vitamin C intake seems to increase the risk of symptomatic nephrolithiasis
Dietary supplements for chronic gout
Andrés M, Sivera F, Buchbinder R +2 more
Allopurinol reduced sUA levels more than vitamin C
Effect of vitamin C and hesperidin on serum uric acid concentrations in healthy adults with high uric acid levels: the randomized controlled 'HesperidrinC trial'
Enderle J, Dörner R, Tondar D +4 more
Vitamin C but not hesperidin decreased serum uric acid levels
Genetically high plasma vitamin C and urate: a Mendelian randomization study in 106 147 individuals from the general population
Kobylecki CJ, Afzal S, Nordestgaard BG
our data do not support a causal relationship between high plasma vitamin C and low plasma urate
Vitamin C intake and the risk of gout in men: a prospective study
Choi HK, Gao X, Curhan G
Higher vitamin C intake is independently associated with a lower risk of gout
Determinants of 24-hour urinary oxalate excretion
Taylor EN, Curhan GC
Participants consuming 1000 mg/d or more of vitamin C excreted 6.8 mg/d more urinary oxalate
Vitamin C intake and serum uric acid concentration in men
Gao X, Curhan G, Forman JP +2 more
vitamin C intake in men is inversely associated with serum uric acid concentrations
Ascorbic Acid Supplements and Kidney Stones Incidence Among Men and Women: A systematic review and meta-analysis
Jiang K, Tang K, Liu H +3 more
AA supplements was remarkably correlated with higher risk for kidney stones incidence in men
Effect of vitamin C supplements on urinary oxalate and pH in calcium stone-forming patients
Baxmann AC, De O G Mendonça C, Heilberg IP
vitamin C supplementation may increase urinary oxalate excretion and the risk of calcium oxalate crystallization
Vitamin C intake and multiple health outcomes: an umbrella review of systematic reviews and meta-analyses
Xu K, Peng R, Zou Y +3 more
Harmful associations were found for breast cancer and kidney stones for vitamin C supplement intake
Effect of vitamin B2, vitamin C, vitamin D, vitamin E and folic acid in adults with essential hypertension: a systematic review and network meta-analysis
Qi S, Luo X, Liu S +3 more
Among the five vitamins, only vitamin E was significantly more effective at reducing SBP
Exploring the causal associations of micronutrients on urate levels and the risk of gout: A Mendelian randomization study
Qiu Y, Li C, Huang Y +4 more
No clear associations were found between the other micronutrients and the urate levels
Diet-Derived Antioxidants and Risk of Kidney Stone Disease: Results From the NHANES 2007-2018 and Mendelian Randomization Study
Jian Z, Wang M, Jin X +2 more
Our study did not support a causal association between circulating antioxidants levels and KSD risk
Is it safe to prescribe ascorbic acid for urinary acidification in stone-forming patients with alkaline urine?
Noureldin YA, da Silva A, Fahmy N +1 more
Eight (33.3%) patients developed de novo urolithiasis
Relation of serum ascorbic acid to serum vitamin B12, serum ferritin, and kidney stones in US adults
Simon JA, Hudes ES
We found no association between serum ascorbic acid level and prevalence of kidney stones
Association between vitamins intake and kidney stone: A cross-sectional study
Li D, Li S
more intake of vitamin C and E may be associated with a lower prevalence of KS
Clinically Insignificant Effect of Supplemental Vitamin C on Serum Urate in Patients With Gout: A Pilot Randomized Controlled Trial
Stamp LK, Frampton C, O Donnell JL +2 more
Studies in human volunteers have shown that vitamin C reduces serum urate (SU) levels. The aim of this study was to determine the effects of vitamin C on SU levels in patients with gout.
Serum Ascorbic Acid and Gallbladder Disease Prevalence Among US Adults: The Third National Health and Nutrition Examination Survey (NHANES III)
Simon JA, Hudes ES
To examine the relationship of ascorbic acid, an antioxidant nutrient involved in cholesterol catabolism, to gallbladder disease, we analyzed data collected from a probability sample of US adults.
Age-related cataract in a randomized trial of vitamins E and C in men
Christen WG, Glynn RJ, Sesso HD +2 more
For vitamin C, there were 593 cataracts in the treated group and 581 in the placebo group (hazard ratio, 1.02; 95% confidence interval, 0.91-1.14).
Vitamin C for preventing and treating the common cold
Hemila H, Chalker E
Regular supplementation had a modest but consistent effect in reducing the duration of common cold symptoms... in five trials with participants under heavy short-term physical stress, the common cold risk was halved.
Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones
Ferraro PM, Curhan GC, Gambaro G +1 more
Total and supplemental vitamin C intake was significantly associated with higher risk for incident kidney stones in men, but not in women.
Antioxidant vitamins supplementation reduce endometriosis related pelvic pain in humans: a systematic review and meta-analysis
Zheng SH, Chen XX, Chen Y +3 more
antioxidant vitamins supplementation reduce endometriosis related pelvic pain in humans
The efficacy and safety of vitamin C for iron supplementation in adult patients with iron deficiency anemia: a randomized clinical trial
Li N, Zhao G, Wu W
Among patients with IDA, oral iron supplements alone were equivalent to oral iron supplements plus vitamin C in improving hemoglobin recovery and iron absorption.
Efficacy of topical vitamin C in melasma and photoaging: A systematic review
Correia G
Topical vitamin C may be a suitable alternative for melasma and photoaging, but more studies are needed.
Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases
Bjelakovic G, Nikolova D, Gluud LL +2 more
vitamin C (3637 dead/36,659 (9.9%) versus 2717 dead/29,283 (9.3%); 29 trials, RR 1.02, 95% CI 0.98 to 1.07)
Antioxidant vitamin supplementation prevents oxidative stress but does not enhance performance in young football athletes
de Oliveira DCX, Rosa FT, Simões-Ambrósio L +1 more
Antioxidant vitamin supplementation prevents oxidative stress but does not enhance performance in young football athletes.
Scurvy: reemergence of nutritional deficiencies
Leger D
Easy bruising and bleeding gums from vitamin C deficiency resolve rapidly with repletion.
Effects of vitamin C on dark circles of the lower eyelids: quantitative evaluation using image analysis and echogram
Ohshima H, Mizukoshi K, Oyobikawa M
Topical vitamin C application increased the thickness of the lower eyelid dermis and reduced the dark appearance caused by underlying vasculature.
Antioxidant therapies for obstructive sleep apnea: A systematic review and meta-analysis
Boppana TK
Antioxidant therapy in patients with OSA is associated with improved endothelial function, reduced oxidative stress, and improved sleep parameters.
Antioxidant vitamin C improves endothelial function in obstructive sleep apnea
Grebe M
The reduced endothelial-dependent vasodilation in untreated patients with OSA acutely improves by the free radical scavenger vitamin C.
Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration
Antioxidant vitamin formulations including vitamin C slowed progression of age-related macular degeneration.
Current treatment for male infertility: an umbrella review of systematic reviews and meta-analyses
Ye JJ, Chen ZY, Wang QH +4 more
Antioxidant supplements improved semen parameters, but evidence for live birth outcomes remained weak.
Phlebotonics for venous insufficiency
Martinez-Zapata MJ, Vernooij RW, Simancas-Racines D +5 more
Flavonoid phlebotonics reduced symptoms of capillary fragility in chronic venous insufficiency.
Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial
Sesso HD, Buring JE, Christen WG +7 more
There also was no significant effect of vitamin C on major cardiovascular events.
Vitamin C supplements and the risk of age-related cataract: a population-based prospective cohort study in women
Rautiainen S, Lindblad BE, Morgenstern R +1 more
The multivariable hazard ratio (HR) for vitamin C supplement users compared with that for nonusers was 1.25 (95% CI: 1.05, 1.50).
Efficacy of vitamins C, E, and their combination for treatment of restless legs syndrome in hemodialysis patients: A randomized, double-blind, placebo-controlled trial
Sagheb MM
Vitamins C and E and their combination are safe and effective treatments for reducing the severity of RLS in hemodialysis patients over the short-term.
A prospective study of the intake of vitamins C and B6, and the risk of kidney stones in men
Curhan GC, Willett WC, Rimm EB +1 more
These data do not support an association between a high daily intake of vitamin C or vitamin B6 and the risk of stone formation, even when consumed in large doses.
A double-blind placebo-controlled trial of antioxidant therapy in limited cutaneous systemic sclerosis
Herrick AL, Hollis S, Schofield D
No clinical benefit could be demonstrated from active treatment. There are several possible explanations for this negative result, including the short duration of therapy. It is possible that antioxidant therapy, to be effective, needs to be given early in the SSc disease process, before the onset of irreversible tissue damage.
Foodstate vitamin C complex may beneficially affect haemostasis and fibrin network structure in hyperlipidaemic patients
Supplementation for 8 weeks with a FoodState Vitamin C complex may improve haemostatic factors and fibrin network structures.
Does combined antioxidant vitamin supplementation blunt repeated bout effect?
He F, Hockemeyer JA, Sedlock D
Overall, DOMS of the quadriceps was lower in S (1.1±0.3) than P (2.2±0.5) (P<0.05).
Vitamin C supplement use may protect against gallstones: an observational study on a randomly selected population
Walcher T, Haenle MM, Kron M +3 more
Vitamin C supplement use may protect against gallstones: an observational study on a randomly selected population.
Vitamin C and immune function
Carr AC, Maggini S
Vitamin C contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune system.
Assessment of the use of vitamin C and E supplements concomitantly to antibiotic treatment against Helicobacter pylori: A systematic review and meta-analysis.
Caicedo Ochoa EY, Quintero Moreno CO, Mendez Fandino YR +1 more
Without discriminating the number of antibiotics used, there was no relationship with the eradication of the infection (OR: 1.98 [95%CI: 0.92-4.29] P=.08).
Impact of micronutrient deficiency & malnutrition in systemic sclerosis: Cohort study and literature review
Dupont R, Longue M, Galinier A +1 more
Se testing should be considered as soon as cardiac involvement is suspected. VitC testing should be considered in malnourished SSc patients, especially if skin involvement is extensive.
Short-Term High-Dose Vitamin C and E Supplementation Attenuates Muscle Damage and Inflammatory Responses to Repeated Taekwondo Competitions: A Randomized Placebo-Controlled Trial
Chou CC, Sung YC, Davison G +2 more
Short-term high-dose vitamin C and E supplementation attenuates muscle damage, hemolysis, and inflammatory responses to repeated taekwondo competitions.
Vitamin C and Immune Function
Carr AC, Maggini S
Vitamin C accumulates in leukocytes and supports NK cell and phagocyte function
Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trial
Kim TK, Lim HR, Byun JS
The vitamin C group had a 0.80-fold lower risk of getting a common cold than did the placebo group.
Effects of ascorbic acid supplementation on serum progesterone levels in patients with a luteal phase defect
Henmi H, Endo T, Kitajima Y +3 more
Serum progesterone rose significantly in the vitamin C group compared with untreated controls
Role of vitamin C and E supplementation on IL-6 in response to training
Yfanti C, Fischer CP, Nielsen S +7 more
Although vitamin C and E supplementation may attenuate exercise-induced increases in plasma IL-6 there is no clear additive effect when combined with endurance training.
In overweight and obese women, dietary iron absorption is reduced and the enhancement of iron absorption by ascorbic acid is one-half that in normal-weight women
Cepeda-Lopez AC, Melse-Boonstra A, Zimmermann MB +1 more
Geometric mean iron absorptions were 29.5% in normal-weight and 16.6% in overweight and obese women from meals with ascorbic acid.
Are antioxidant supplements effective in reducing delayed onset muscle soreness? A systematic review
Candia-Luján R, De Paz Fernández JA, Costa Moreira O
Both vitamins and commercial supplements have low effectiveness in reducing DOMS, while polyphenols and other antioxidant supplements show moderate to good effectiveness in combating DOMS.
Antioxidant vitamins and magnesium and the risk of hearing loss in the US general population
Choi YH, Miller JM, Tucker KL +2 more
High intakes of beta-carotene or vitamin C combined with high magnesium compared with low intakes of both nutrients were significantly associated with lower (better) PTAs at high frequencies.
Lack of effect of experimental ascorbic acid deficiency on bile acid metabolism, sterol balance, and biliary lipid composition in man
Jenkins SA, Taylor W, Blackstone MO
Experimentally induced ascorbic acid deficiency did not significantly alter bile acid metabolism, sterol balance, or biliary lipid composition in man.
Effect of ascorbic acid intake on nonheme-iron absorption from a complete diet
Cook JD, Reddy MB
There was no significant difference in mean iron absorption among the 3 dietary periods despite a range of mean daily intakes of dietary vitamin C of 51-247 mg/d.
The Roles of Vitamin C in Skin Health
Pullar JM, Carr AC, Vissers MC
Vitamin C is an essential cofactor for collagen hydroxylation and supplementation supports dermal collagen formation
Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis
Shaw G, Lee-Barthel A, Ross ML +2 more
Vitamin C-enriched gelatin before loading doubled blood markers of collagen synthesis
The roles of vitamin C in skin health
Pullar JM, Carr AC, Vissers MCM
Normal skin contains high concentrations of vitamin C, which supports important and well-known functions, stimulating collagen synthesis and assisting in antioxidant protection against UV-induced photodamage.
A phase 3 randomized trial of nicotinamide for skin-cancer chemoprevention
Chen AC, Martin AJ, Choy B
Nicotinamide reduced new non-melanoma skin cancers by 23% versus placebo
Safety Information
Potential Side Effects
{"Nausea and loose stools above ~2 g/day (osmotic effect)","Heartburn in sensitive individuals","Kidney stone risk with chronic megadoses in susceptible people"}
Contraindications
Hemochromatosis, glucose-6-phosphate dehydrogenase deficiency
Drug Interactions
- Aluminum-containing antacids
- Chemotherapy drugs
- Estrogen
Pregnancy & Breastfeeding
Pregnancy: Considered safe
Breastfeeding: Considered safe
Dosage Guidelines
Dosage Used in Studies
500-2000 mg
Best Time to Take
Split doses throughout day
Best Form
Ascorbic acid or mineral ascorbates
Bioavailability
Dose-dependent: near-complete below 200 mg, falling to under 50% above 1 g. Plasma saturates around 200-400 mg/day; excess is excreted renally.
Dosing by Goal
| Goal | Dose | Notes |
|---|---|---|
| General health | 100-200 mg daily (or simply meet the RDA: 75 mg women / 90 mg men) | Beyond ~200 mg/day plasma levels plateau. Split doses if taking more. |
| Cold season / heavy training blocks | 200-500 mg daily, started before exposure | Regular use matters — starting vitamin C after symptoms begin shows little benefit. |
| With iron supplementation | 50-100 mg alongside each iron dose | Improves non-heme iron absorption meaningfully; orange juice works too. |
Forms Compared
Ascorbic acid
Best for Almost everyone
The cheapest and most studied form. No clinical advantage has been demonstrated for fancier forms in healthy people.
Buffered (sodium/calcium ascorbate)
Best for Sensitive stomachs
Less acidic; useful if plain ascorbic acid causes heartburn or GI upset.
Liposomal
Best for Unclear
Marketed for absorption, but plasma saturation kinetics limit the practical benefit; costs several times more.
Ester-C / ascorbates with metabolites
Best for Unclear
Marketing claims outpace trial data; no demonstrated superiority.
Food & Timing
With meals if GI-sensitive; always pair with iron-rich meals or iron supplements when correcting deficiency.
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Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.