Vitamin C for the prevention and treatment of coronavirus

  • 5 Jul 2020
  • Reading time 8 mins
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COVID-19, or SARS-CoV-2, is a coronavirus disease, classified as influenza, although coronaviruses can also induce colds, both of which are upper respiratory tract infections (URTIs). The consequences of infection can be pneumonia, hospitalisation in Intensive Care Units (ICUs), mechanical ventilation often as a consequence of cytokine storm/sepsis, and resultant organ failure and death.

As a prelude to studies specifically on COVID-19 patients studies on vitamin C and any of conditions mentioned above are relevant to decisions as to the suitability of using vitamin C both for prevention of COVID-19, a potential therapy, and for further research.



Vitamin C for coronavirus prevention with daily vitamin C supplementation

In a 2013 meta-analysis of 29 controlled trials with 11,306 participants, H.Hemilä showed that regular vitamin C intake of around 1 g/day did not prevent upper respiratory tract infections (URTIs).[1] However, the same trials found that vitamin C did shorten and alleviate URTIs that occurred during the period of vitamin C administration. In adults the duration of infections was reduced by 8% (approx half a day) and in children by 14% (approx 1 day).[2]

The last UK placebo controlled trial (2002) best illustrates the meaningful clinical difference between number of colds, cold duration and severity. One hundred sixty-eight volunteers were randomized to receive a placebo or a vitamin C supplement, two 500mg tablets daily, over a 60-day period between November and February. The researchers used a five-point scale to assess their health and recorded any common cold infections and symptoms in a daily diary. Compared with the placebo group, the vitamin C treatment group had fewer colds (37 vs 50, P<.05), but even fewer virally challenged ‘cold’ days (85 vs 178) and a shorter duration of severe symptom days (1.8 vs 3.1 days, P<.03). The number of participants who had 2 colds during their trial (2/84 on vitamin C vs 16/84 in the placebo group; P = .0004).[3]

The evidence for a significant reduction in duration and severity of colds is greater and more consistent with a intake of 2 or more g/day. Given that COVID-19 is often much more severe than ordinary URTIs, the above estimates might justify a regular increased daily intake of vitamin C of at least 2 g/day while the prevalence of COVID-19 is high, and even more during an infection.

Vitamin C for coronavirus treatment - taking vitamin C during infection

While a relatively small amount of vitamin C is sufficient for healthy people the effective use of vitamin C depends of how much is required to support the immune system. When a person is infected the amount required increases dramatically. This is illustrated by the depletion of vitamin C levels in leucocytes, critical for immune response, during colds and flu. These critical immune cells normally have more than 10-fold higher vitamin C levels than other cells. An intake of 6 g/day has been shown to restore normal vitamin C levels in leucocytes during colds.[4] This suggests that similar daily doses may be required to have a symptom reducing effect. Studies giving 3 vs 6[5] or 4 vs 8 g/day[6] have shown the higher the dose the greater the effect with a 20% decrease in cold duration with 6 to 8 g/day. This equates to 1.5 to 2 days shorter colds. However, 46% of those taking 8 g/day in the first day of a cold report being symptom free after 24 hours. Case reports indicate greater effect with doses of 15+ g/day, titrating the dose to ‘bowel tolerance’ levels.[7] During infection most people can tolerate 1 g/hr without diarrhoea. This was Dr Linus Pauling’s recommendation – to start with a loading dose of 2 or 3 g, then take 1g/hr until symptoms disappear.

Vitamin C for hospitalised & ICU patients with pneumonia, sepsis or COVID-19

Vitamin C supplementation has been shown effective, even at low doses between 0.2g and 1.6 g/day, in reducing incidence, speeding up recovery and reducing mortality in those with pneumonia.[8] A recent study by A.Carr has reported depleted plasma vitamin C status (23µmol/l) in 44 hospitalised patients with pneumonia, compared to healthy controls (56µmol/l).[9] The most severe patients in ICU had levels averaging 11µmol/l, which is the level that defines scurvy.

P.Marik has reported similar findings in 22 ICU patients with sepsis with levels of 14.1nmol/l [10] and recommends giving 1.5 g of vitamin C every 6 hours intravenously.[11] Marik has also reported that all COVID-19 patients in ICUs so far tested by his group (Frontline Covid-19 Critical Care - FLCCC) have deficient or undetectable levels of vitamin C sufficient to diagnose scurvy.[12]

M.Vizcachipi, at the Chelsea and Westminster NHS Hospital, using 1g vitamin C every 12 hours, has reported a mortality rate (25.1% in females and 38.2% in males) 21% lower than the UK national average (ICNARC data) of 49%, thus saving one in five lives.[13]

Vitamin C to prevent or shorten ICU hospitalisation, mechanical ventilation and mortality

One of the major causes for concern with COVID-19 is the relatively high proportion of cases requiring intensive care unit (ICU) treatment. H.Hemila’s meta-analysis of 12 trials with 1,766 non-COVID patients in ICU found that vitamin C shortened ICU stay by 8%.[14] Another meta-analysis of eight trials found that vitamin C shortened the duration of mechanical ventilation in patients who required the longest ventilation.[15]

There is evidence that vitamin C levels decline precipitously in critically ill patients and that administration of an appropriate dose can dramatically reduce complications and mortality.[16] Although 0.1 g/day of vitamin C can maintain a normal plasma level in a healthy person, much higher doses (1 – 4 g/day) are needed to increase plasma vitamin C levels of critically ill patients to within the normal range[17]. The FLCCC give 3 g of intravenous vitamin C every six hours, together with steroids and anti-coagulants. FLCCC are reporting zero COVID-19 deaths in their ICUs in those without end-stage comorbidities.[18]

Preliminary, unpublished results of a randomised, placebo controlled trial in Wuhan of mechanically ventilated ICU patients given either 12 g of intravenous vitamin C twice daily or sterile water placebo in a saline drip show 24% mortality on the vitamin C group vs 35% in the placebo group, with significant results in the reduction of the inflammatory marker IL-6 and of mortality in those with the worst pulmonary function index (PF<150).[19]


Overall, a variety of studies have shown that high-dose oral supplements of vitamin C can reduce the risk of infection and effectively reduce the intensity of viral infections, and in a hospital ICU setting high-dose oral and IV vitamin C in combination with a well-established critical care protocol can treat COVID-19 to prevent serious pneumonia, need for mechanical ventilation, organ failure, septic shock, and death. 





[1] Hemilä H, Chalker E. (2013) Vitamin C for preventing and treating the common cold.
Cochrane Database Syst Rev. 2013 Jan 31;(1):CD000980.


[2] See Hemilä above

[3] Van Straten, M., Josling, P. Preventing the common cold with
a vitamin C supplement: A double-blind, placebo-controlled survey. Adv
Therapy 19, 151 (2002).

[4] Hume, R.;Weyers, E. Changes in
leucocyte ascorbic acid during the common cold. Scott. Med. J. 1973, 18,


[5] Karlowski, T.R.; Chalmers, T.C.; Frenkel, L.D.; Kapikian, A.Z.; Lewis, T.L.; Lynch, J.M. Ascorbic acid for the common cold: A prophylactic and therapeutic trial. JAMA 1975, 231, 1038–1042.

[6] Anderson, T.W.; Suranyi, G.; Beaton, G.H. The effect on winter illness of large doses of vitamin C. Can.
Med. Assoc. J. 1974, 111, 31–36.


[8] Hemilä H Vitamin C and Infections Nutrients. 2017 Apr; 9(4): 339.

[9]  Carr  AC et al., ‘Patients with community acquired pneumonia exhibit depleted vitamin C status and elevated oxidative stress’ Nutrients 2020, 12, 1318; doi:10.3390/nu12051318

[10] Marik’s source of vit C levels in sepsis data

[11] Marik and Hooper Critical Care (2018) 22:23 DOI 10.1186/s13054-018-1950-z

[12] Awaiting publication. See data, reported by Dr Paul Marik in podcast:

[13] Vizcachipi M,  Preprint at

[14] Hemilä H, Chalker E. Vitamin C can shorten the length of stay in the ICU: a meta-analysis. Nutrients 2019;11:E708

[15] Hemilä H, Chalker E. Vitamin C may reduce the duration of mechanical ventilation in critically ill patients: a meta-regression analysis. J Intensive Care 2020;8:15.

[16] Carr AC, Rosengrave PC, Bayer S, Chambers S, Mehrtens J, Shaw GM. Hypovitaminosis C and vitamin C deficiency in critically ill patients despite recommended enteral and parenteral intakes. Crit Care 2017;21:300; see also ref 12 above.

[17] de Grooth HJ, Manubulu-Choo WP, Zandvliet AS, Spoelstra-de Man AM, Girbes AR, Swart EL, Oudemans-van Straaten HM. Vitamin C pharmacokinetics in critically ill patients: a randomized trial of four IV regimens. Chest 2018;153:1368–1377.; see also ref 12 above.

[18] See

[19] Personal communication from Dr Z. Peng, 10th April 2020. Publication pending.