TORONTO -- Reports that hospitals are turning to high doses of intravenous vitamin C to treat patients with severe cases of COVID-19 have reignited claims that the vitamin can prevent or cure cases of the novel coronavirus.

Though vitamin C has long been touted as an immune-boosting vitamin, experts warn that its potential for treating coronavirus has not been proven. In fact, there is conflicting evidence to support the vitamin’s use as a treatment for the common cold or flu.

Here is what you need to know about the claims involving vitamin C and COVID-19:


Yes, some critically ill patients have been treated with high-dose intravenous vitamin C. However, there has yet to be any clear scientific evidence that this is an effective treatment for the virus.

A study involving 140 coronavirus patients in Wuhan, China, the epicentre of the virus, is currently underway to determine the effectiveness of high-dose vitamin C in patients with severe acute respiratory infections.

As part of the study, patients will receive 12 grams of vitamin C by IV twice per day -- significantly more than the 75 to 90 milligram daily allowance recommended by Health Canada for the average adult.

The study is not expected to be completed until fall and no findings have been published.

Health Canada confirmed to Thursday that it recently authorized a clinical trial to investigate the use of intravenous vitamin C in COVID-19 patients, “to help improve the functioning of some of the body’s organs that is associated with severe cases of COVID-19.”

The health agency said it will “closely monitor” the trial’s progress, noting that it has expedited its regulatory process for any COVID-19 related health products, including the review of submissions and the authorization of clinical trials.

“Currently, there are no drugs specifically authorized to treat COVID-19 since it is still a relatively new virus,” a Health Canada spokesperson said via email.

But the spokesperson notes that for drugs showing "early promise" in treating the virus, the best way to develop new therapies is through clinical trials, allowing the healthcare community to "systematically collect information on the effectiveness of the treatments and what the associated risks may be.”​​

"When you don't have any kind of effective medication, as we don't have for COVID-19, you pull out all the plugs and try everything. That’s what the Chinese trial is doing," Joe Schwarcz, director of McGill University’s Office for Science and Society, told by phone on Monday.

"But this is a long way from people asking whether or not they should be taking huge doses of vitamin C to try to prevent infection by this virus. There is zero evidence for that."

It has also been reported that hospitals in New York, Wisconsin, and Virginia are testing similar protocols involving high-dose intravenous vitamin C.

However, as Schwarcz notes, aside from observations there is not yet enough scientific data to prove its effectiveness.

The World Health Organization, which regularly updates its database of clinical trials and research regarding COVID-19, has yet to specifically mention high-dose vitamin C.

However, the global health authority’s website states, "While there are a number of therapeutics currently in clinical trials in China and more than 20 vaccines in development for COVID-19, there are currently no licensed vaccines or therapeutics for COVID-19."

Earlier this week, Australia’s department of health released a statement regarding the use of high-dose vitamin C noting, "we have investigated this report and found there is no robust scientific evidence to support the usage of this vitamin in the management of COVID-19."

The statement adds non-peer reviewed studies related to the use of high-dose intravenous vitamin C for acute respiratory distress syndrome presented "no clear benefit."


The idea that high-dose intravenous vitamin C might help in curbing infections is not new.

A 2019 study looked at the effects of high-dose vitamin C infusions in patients suffering from sepsis and acute respiratory distress syndrome, the most common conditions leading to ICU admission, ventilator support, or death among those with severe COVID-19 infections, according to Harvard University.

The study found that while organ function, inflammation markers and vascular injuries did not significantly improve over the first four days of treatment, there was a lower death rate observed within 28 days among those that received the vitamin C infusion.

Aileen Burford-Mason, an immunologist and cell biologist, says that high-dose intravenous vitamin C has been used by hospitals to treat viral infections amid suggestions it can help repair damaged lung tissue.

The biggest caveat, she notes, is that administering vitamin C intravenously allows for patients to receive much higher doses than usually recommended.

Vitamin C is an essential nutrient; however, unlike most animals, humans don’t produce it on their own. Traditionally, we rely on our diet to get our daily intake. Its required to product collagen, an essential component of connective tissue and wound healing and plays has important antioxidant functions.

According to the U.S. National Institutes of Health (NIH), ongoing research is examining whether vitamin C can limit the development certain cancers, cardiovascular disease, and other diseases.

Yet, while the NIH says it plays an important role on immune function, it notes there is conflicting evidence to suggest it can prevent or reduce the risk or severity of colds and flus -- one of the most common claims made about vitamin C.

"The evidence to date suggests that regular intakes of vitamin C at doses of at least 200 mg/per day do not reduce the incidence of the common cold in the general population," reads its website.

The NIH does suggest that vitamin C supplements might shorten the duration of the common cold and alleviate the severity of symptoms.


As Harvard University experts note, there is no current scientific evidence that taking vitamin C will help prevent COVID-19.

But that hasn’t stopped an onslaught of social media posts and online article recommending that people increase their daily intake to boost immunity in light of the virus.

Health Canada recommends 90 mg per day of vitamin C for the average adult male and 75 mg per day for the average woman. The tolerable upper intake level (UL), the highest daily intake likely to pose no risks, for adults is 2,000 mg per day.

Most of the vitamin C supplements, such as the chewable tablets many opt for, range from about 500 to 1,000 mg per serving.

Standard doses of vitamin C are generally harmless because it’s a water-soluble vitamin, which means any excess is generally excreted in the urine. But high doses can cause a number of side effects, including diarrhea, nausea, cramps, and an increased risk of kidney stones.

Daily recommended dose of vitamin C