Editing Vitamin C (section)

===COVID-19===
{{see also|COVID-19 drug repurposing research#Vitamin C|COVID-19 misinformation#Vitamin C}}

During March through July 2020, vitamin C was the subject of more US FDA warning letters than any other ingredient for claims for prevention and/or treatment of COVID-19.<ref name="pmid33001378">{{cite journal |vauthors=Bramstedt KA |title=Unicorn poo and blessed waters: COVID-19 quackery and FDA Warning Letters |journal=Ther Innov Regul Sci |date=October 2020 |volume=55 |issue=1 |pages=239–44 |pmid=33001378 |pmc=7528445 |doi=10.1007/s43441-020-00224-1 }}</ref> In April 2021, the US [[National Institutes of Health]] (NIH) COVID-19 Treatment Guidelines stated that "there are insufficient data to recommend either for or against the use of vitamin{{nbsp}}C for the prevention or treatment of COVID-19."<ref name="COVID-19 Treatment Guidelines-2021">{{cite web |title=Vitamin C |url=https://www.covid19treatmentguidelines.nih.gov/therapies/supplements/vitamin-c/ |website=COVID-19 Treatment Guidelines |date=April 21, 2021 |access-date=January 2, 2022 |archive-date=November 20, 2021 |archive-url=https://web.archive.org/web/20211120131306/https://www.covid19treatmentguidelines.nih.gov/therapies/supplements/vitamin-c/ |url-status=live }}</ref> In an update posted December 2022, the NIH position was unchanged:
* There is insufficient evidence for the COVID-19 Treatment Guidelines Panel (the Panel) to recommend either for or against the use of vitamin C for the treatment of COVID-19 in nonhospitalized patients.
* There is insufficient evidence for the Panel to recommend either for or against the use of vitamin C for the treatment of COVID-19 in hospitalized patients.<ref name="U.S. National Institutes of Health-2022">{{cite web |url=https://www.covid19treatmentguidelines.nih.gov/therapies/supplements/vitamin-c/ |title=COVID-19 treatment guidelines |date=December 26, 2022 |website=U.S. National Institutes of Health |access-date=December 18, 2023 |archive-date=November 20, 2021 |archive-url=https://web.archive.org/web/20211120131306/https://www.covid19treatmentguidelines.nih.gov/therapies/supplements/vitamin-c/ |url-status=live }}</ref>

For people hospitalized with severe COVID-19 there are reports of a significant reduction in the risk of all-cause, in-hospital mortality with the administration of vitamin C relative to no vitamin C. There were no significant differences in ventilation incidence, hospitalization duration or length of intensive care unit stay between the two groups. The majority of the trials incorporated into these meta-analyses used intravenous administration of the vitamin.<ref name=Kow2023>{{cite journal |vauthors=Kow CS, Hasan SS, Ramachandram DS |title=The effect of vitamin C on the risk of mortality in patients with COVID-19: a systematic review and meta-analysis of randomized controlled trials | journal=Inflammopharmacology |volume=31 |issue=6 |pages=3357–62 |date=December 2023 |pmid= 37071316|pmc=10111321 |doi=10.1007/s10787-023-01200-5 |url=}}</ref><ref name=Huang2022>{{cite journal |vauthors=Huang WY, Hong J, Ahn SI, Han BK, Kim YJ |title=Association of vitamin C treatment with clinical outcomes for COVID-19 patients: A systematic review and meta-analysis |journal=Healthcare |volume=10 |issue=12 |date=December 2022 |page=2456 |pmid=36553979 |pmc=9777834 |doi=10.3390/healthcare10122456 |url= | doi-access = free | title-link = doi }}</ref><ref name=Olczak2022>{{cite journal |vauthors=Olczak-Pruc M, Swieczkowski D, Ladny JR, Pruc M, Juarez-Vela R, Rafique Z, Peacock FW, Szarpak L |title=Vitamin C supplementation for the treatment of COVID-19: A systematic review and meta-analysis |journal=Nutrients |volume=14 |issue=19 |date=October 2022 |page=4217 |pmid=36235869 |pmc=9570769 |doi=10.3390/nu14194217 |url= | doi-access = free | title-link = doi }}</ref> Acute kidney injury was lower in people treated with vitamin C treatment. There were no differences in the frequency of other adverse events due to the vitamin.<ref name=Olczak2022 /> The conclusion was that further large-scale studies are needed to affirm its mortality benefits before issuing updated guidelines and recommendations.<ref name=Kow2023 /><ref name=Huang2022 /><ref name=Olczak2022 />