Vitamin C (L-ascorbic acid) is a water-soluble vitamin that humans cannot synthesise; it is a cofactor for collagen, carnitine and neurotransmitter synthesis.
What published studies and recent community write-ups report about amounts, timing and course length. 5 clinical and 2 community-reported rows, each linked to its source. These are descriptions of what others report, not instructions, and nothing here is medical advice.
| Context | Dose | Frequency | Route | Course | Source |
|---|---|---|---|---|---|
| Clinical5 rows | |||||
| Recommended intakes and upper limit (NIH reference)General population; smokers need 35 mg a day more | RDA 90 mg a day for men and 75 mg for women (85 mg in pregnancy, 120 mg in lactation); upper limit 2,000 mg a day for adults | Daily intake from food and supplements combined | Oral | LifelongNot applicable | Office of Dietary Supplements, National Institutes of Health2025 |
| About 70-90% of a 30-180 mg intake is absorbed, but above 1 g a day absorption falls below 50% and the excess is excreted, so even 3 g every four hours is predicted to peak plasma at only 220 micromolar; intravenous dosing can reach 26,000 micromolar. Scurvy appears within about a month of intakes below 10 mg a day. High oral doses mainly cause diarrhoea and gastrointestinal upset, with kidney stones a concern in people with pre-existing hyperoxaluria. | |||||
| Prescription injection label (ascorbic acid 500 mg/mL)Adults and children from 5 months with signs and symptoms of scurvy who cannot take vitamin C by mouth | 200 mg once daily for adults and children 11 and older; 100 mg for ages 1-10; 50 mg for infants 5-11 months | Once daily | Slow intravenous infusion after dilution to 1-25 mg/mL in an isotonic solution | Up to 7 days, repeated only if scurvy symptoms have not improvedNot applicable | DailyMed, National Library of Medicine2026 |
| The approved label is narrow: it covers short-term scurvy treatment only, states that the product is not indicated for deficiency without scurvy, and warns that the 25,000 mg pharmacy bulk vial must never be given to one patient. It lists oxalate nephropathy and kidney stones with prolonged high doses, haemolysis in G6PD deficiency, and interference with glucose and other redox-based laboratory tests for 24 hours after infusion. The gram-scale infusions used in trials are off-label. | |||||
| LOVIT trial in septic shock (harm signal)872 adults with proven or suspected infection who were receiving a vasopressor in the intensive care unit | 50 mg/kg of body weight per infusion | Every 6 hours | Intravenous infusion | Up to 96 hoursNot applicable | New England Journal of Medicine (PubMed)2022 |
| Death or persistent organ dysfunction at day 28 occurred in 44.5% of the vitamin C group against 38.5% on placebo (risk ratio 1.21), with 28-day mortality 35.4% versus 31.6%, and one serious anaphylaxis and one severe hypoglycaemia in the treated group. This is the largest randomised trial of high-dose intravenous vitamin C and it pointed toward harm, not benefit, in this population. | |||||
| CITRIS-ALI trial in sepsis with acute respiratory distress syndrome167 patients with sepsis and ARDS in 7 US medical intensive care units | 50 mg/kg in 5% dextrose | Every 6 hours | Intravenous infusion | 96 hoursNot applicable | JAMA (PubMed)2019 |
| Organ failure scores, C-reactive protein and thrombomodulin, the three primary outcomes, did not differ from placebo over 96 hours. A lower 28-day mortality in the vitamin C arm was one of many secondary outcomes and is widely cited, but the trial failed its primary endpoints and the later, larger LOVIT trial did not confirm a survival benefit. | |||||
| Randomised phase 2 trial in metastatic pancreatic cancer36 patients with stage IV pancreatic adenocarcinoma randomised to gemcitabine and nab-paclitaxel with or without ascorbate; 34 treated | 75 g per infusion | Three times weekly | Intravenous infusion alongside standard chemotherapy | For the duration of chemotherapyNot described | Redox Biology (PubMed)2024 |
| Median overall survival was 16 months with ascorbate against 8.3 months with chemotherapy alone, and progression-free survival 6.2 against 3.9 months, without added toxicity or worse quality of life; infusions raised serum ascorbate from micromolar to millimolar levels. With 17 patients per arm the confidence intervals are wide, and the authors call for a larger trial before this changes practice. | |||||
| Community-reported2 rows | |||||
| Infusion clinic menu (community) | 25, 50, 75 or 100 g per infusion | Per visit; frequency set after a nurse practitioner review | Intravenous, in a 500 mL fluid base with electrolytes | Visits of about 60-90 minutes; no course length statedNot stated | Community resource2026 |
| A mobile infusion company's menu, included to show what is sold outside trials: doses up to 100 g priced from 269 to 785 dollars, a current G6PD test required before approval, and kidney concerns or past stones listed as reasons to pause. The page itself states that high-dose vitamin C is not a cancer treatment and must not replace oncology care; none of these wellness uses has trial support. | |||||
| Vendor liquid format | 200 mg/mL in a 20 mL vial (4,000 mg total); no dose stated | Not stated | Not stated; the vendor disclaimer excludes injection and supplement use | Not statedNot stated | Community resource2026 |
| A vendor claim. The certificate for lot VIC01 reports 99.85% purity by HPLC and a fentanyl screen; the solution is less than half the strength of the 500 mg/mL prescription product and the whole vial holds 4 g, a fraction of a single trial infusion. The product is sold for antioxidant and redox pathway research. | |||||
Plus 2 community resources (dosing guides, forum threads and vendor write-ups), reported above but not linked.
Vitamin C (L-ascorbic acid) is a water-soluble vitamin that humans cannot synthesise; it is a cofactor for collagen, carnitine and neurotransmitter synthesis and the body's main water-phase antioxidant, and its deficiency causes scurvy. The adult RDA is 75-90 mg a day with a tolerable upper intake level of 2,000 mg, and because absorption and renal excretion cap plasma levels at about 220 micromolar, only intravenous infusion reaches the millimolar concentrations studied as pharmacological ascorbate in cancer and sepsis. Large sepsis trials found no benefit and, in the 872-patient LOVIT trial, more death or organ dysfunction, while a 2024 randomised trial of 75 g three times weekly alongside chemotherapy in 34 patients with metastatic pancreatic cancer roughly doubled median survival. The prescription injection is 500 mg/mL and is approved only for a week of scurvy treatment at 200 mg a day; the research solution sold here is 200 mg/mL in a 20 mL vial.
These themes describe recurring questions in published research. They are not claims of effectiveness or recommendations for use.
Cellular aging, redox balance and mitochondrial function.
Innate defense, inflammatory signaling and barrier models.
About 70-90% of a 30-180 mg intake is absorbed, but above 1 g a day absorption falls below 50% and the excess is excreted, so even 3 g every four hours is predicted to peak plasma at only 220 micromolar; intravenous.
The approved label is narrow: it covers short-term scurvy treatment only, states that the product is not indicated for deficiency without scurvy, and warns that the 25,000 mg pharmacy bulk vial must never be given to.
Death or persistent organ dysfunction at day 28 occurred in 44.5% of the vitamin C group against 38.5% on placebo (risk ratio 1.21), with 28-day mortality 35.4% versus 31.6%, and one serious anaphylaxis and one severe.
Organ failure scores, C-reactive protein and thrombomodulin, the three primary outcomes, did not differ from placebo over 96 hours. A lower 28-day mortality in the vitamin C arm was one of many secondary outcomes and.
Study models remain visible so laboratory and animal findings are not mistaken for established human outcomes.
5 protocol rows on this page come from human trials, trial registrations, regulator labels or reviews of human data. Approval status and populations are stated per row.
2 rows record what blogs, vendor write-ups or forums describe for Vitamin C. None has been verified against primary literature.
Sequence, synonyms and registry identifiers as recorded in PubChem, the National Library of Medicine's open chemistry database. Formula, mass and CAS number are summarized at the top of the page.
L-Ascorbic acid, Ascorbic acid, Vitamin C, L(+)-Ascorbic acid, Cevitamic acid, Redoxon, UNII PQ6CK8PD0R
CIWBSHSKHKDKBQ-JLAZNSOCSA-N
(2R)-2-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxy-2H-furan-5-one
7 curated references, each with its journal, year and study model, plus 2 community resources reported but not linked.